The cheapest base fee is not always the cheapest plan

Budget phones and the Korea Post channel

A budget phone operator does not build a network. It rents capacity wholesale from one of the three mobile carriers and sells service on top. Because the network is rented, coverage and call quality match the carrier it rents from. What you give up is usually the retail footprint and the extras, and what you get back is a lower price.

Korea Post's budget phone channel is not a brand of its own. The post office sells plans on behalf of several operators. The company you actually contract with is the operator, not the post office, and billing and support come from that operator. The post office provides the counter.

This site covers the plans on that counter and nothing else. There are many more operators, and any plan not listed with the post office is not here. So we never say the cheapest plan here is the cheapest plan in the country.

We use this list because Korea Post publishes it as machine readable open data with no stated restriction on use, which is why we can pull it and show it as it is. Most other lists are not open that way.

What decides the monthly bill

A plan carries four numbers: the monthly base fee, and the data, call and text allowances. Stay inside the allowances and the base fee is the whole bill.

Go past an allowance and an overage rate applies. Data is priced per megabyte, calls per second, texts per message. The per-second call rate is the one people miss. At 1.98 KRW per second a minute costs 118.8 KRW, so a hundred minutes past the allowance is over ten thousand won.

So the monthly total is the base fee plus the overage times the rate. Run that arithmetic and the base-fee order and the total order flip surprisingly often. A plan two thousand won cheaper that gives one gigabyte less will cost twenty thousand won more the moment you use that gigabyte at 22 KRW per megabyte.

Data overage is what jumps hardest. A gigabyte is 1,024 megabytes, so a rate that looks small is multiplied by a large number. That makes the first question when picking a plan whether the data allowance covers what you use.

The reverse is also true. An allowance far above your usage is money paid in advance. With no overage on either side, all that is left is the base fee, and then the plan with the smaller allowance and the lower fee wins. Which case you are in only shows once you enter your usage.

The rules this site follows

There is one source: the Korea Post budget phone plan service on the public data portal. We pull it once with an issued key, keep the raw response in the repository, and a build script turns it into the form the page reads. The page never asks anywhere at load time, so the data sits at the date shown on the home page.

The Internet Post Office website lists the same plans, but we did not scrape that screen. That site's robots file refuses machine access to everything. When the same agency has opened a machine readable feed on purpose, there is no reason to push past a door marked closed.

The arithmetic is the base fee plus three overage amounts. Overage is your usage minus the allowance, floored at zero. The call overage rate is per second, so minutes are multiplied by 60. Dropping that 60 would show a sixtieth of the real cost to anyone who talks a lot, and erring towards looking cheap is the most harmful direction, so there is a test pinned on exactly that.

Some plans have an empty allowance box. Those are not calculated; we say so instead. Filling the blank with zero counts everything as overage and inflates the bill; filling it with unlimited shrinks it. Both invent a number the source does not have.

A missing overage rate is different. If your usage fits inside the allowance we still calculate, because there is nothing to multiply and the overage really is zero. Treating that as uncalculable would hide perfectly good plans from light users.

Plans we cannot calculate are not dropped from the page. Quietly removing them would make the screen claim it shows everything while we hide the gaps in the data. They sit in their own section with the reason.

Plan names are printed as the data records them. A name containing the word unlimited does not set an allowance. The name is what the company called it, not data.

The usage you enter never reaches the server. What the server counts is how far a visit got: whether the page opened, whether usage was entered, whether a result was seen, whether a link was copied, along with the date, the language and a rough referral label. Which plan you looked at is not recorded.

Finding your own usage

Past bills are the most accurate source. Your carrier's app or website shows data, calls and texts month by month. Look at three or four months rather than one and work from the heaviest, because running over costs more than an unused allowance does.

If bills are hard to reach, the phone itself knows. On Android it is under network and internet, data usage; on iPhone it is under cellular. Note that the iPhone counter keeps accumulating until you reset it, so check the reset date beside it.

Data use varies enormously between people. Someone on wifi at home and at work finishes a month on a few gigabytes; someone watching video on the move gets through tens of gigabytes. That is exactly why the number that matters is yours rather than an average.

Calls are entered in minutes. Budget plan allowances are usually written as a single pool rather than split by network, and the source data has that single column, so this site treats it as one pool too.

Texts are often only a handful now that messaging apps carry most conversations. Verification codes arrive rather than being sent, so they do not count against the allowance. Only messages you send do.

Contracts, prepaid and networks

The contract column holds three values: no-contract postpaid, contract postpaid, and prepaid. No-contract postpaid bills you the following month and you can leave whenever you like. Contract postpaid trades a lower price for a fixed term, and leaving early can mean a penalty.

Prepaid means topping up in advance. It suits short stays or cases where a credit check is awkward. Its base fee is counted differently from postpaid, so be careful comparing a prepaid monthly total with a postpaid one. We use the recorded figures as they are and label the contract type on screen.

The network column is the carrier whose network the operator rents. Coverage and call quality follow that network, so if your current carrier works well where you live, a budget operator on the same network usually behaves the same. Finer terms such as throttled speeds vary by operator and are not in this data.

The type column separates 5G from LTE. 5G plans generally carry higher base fees, and LTE is enough for most uses. If your handset is 5G only the choice narrows, so check what the handset supports first.

You keep your number. Number portability is handled by the new operator rather than by cancelling first. A remaining contract can still leave a penalty, and a handset instalment plan follows you across. This site does not know those amounts and does not count them.

Where people get stuck

If the plan you want is missing, it may simply not be sold through the post office. This list only covers that counter, so plans an operator sells only on its own site are not here. We do not invent plans that are not in the data.

If a plan says it cannot be calculated, its allowance box is empty in the source. Even a name containing the word unlimited does not let us set a number. For those plans, check the terms with the seller directly.

If a total looks far too high, check the data unit. This site treats one gigabyte as 1,024 megabytes, which is how the plan names and the recorded megabytes line up.

If your real bill is lower than the figure here, it is usually a discount. First-month, bundle and card discounts are not in the public data and so not in the arithmetic. If it is higher, an add-on service or a carrier billing charge may have been added.

If the data date is old, plans may have changed since. This site does not fetch live prices. Always confirm today's terms with the seller before signing up.

This site takes no sign-ups and carries no sign-up links. We are paid by no operator, so we have no reason to lift any plan up the list. The order comes from the usage you entered.