yoyakutorikesi no kawari ni, nitteihenkou ni suru.

Japanese very often leaves out the subject when it is clear from context.

So in 予約取消のかわりに、日程変更にする。, the sentence does not explicitly say I, we, or you. Depending on the situation, it could mean:

• I’ll change the date instead of canceling the reservation.
• We’ll change the date instead of canceling the reservation.
• Please make it a date change instead of a cancellation.
  if used in a service or instruction context

This is completely normal in Japanese.

のかわりに means instead of in this sentence.

The basic idea is:

• A のかわりに B = B instead of A

So here:

• 予約取消のかわりに = instead of canceling the reservation
• 日程変更にする = make it a schedule/date change

Together: Instead of canceling the reservation, [I’ll/we’ll] change the date.

Also, かわりに can have other meanings in other contexts, such as in exchange for or as a substitute for, but instead of is the natural meaning here.

The の connects the noun phrase 予約取消 to かわりに.

Since 予約取消 is being treated as a noun, you use:

• noun + のかわりに

Examples:

• 車のかわりに電車で行く。
  Go by train instead of by car.
• キャンセルのかわりに日程変更をする。
  Do a date change instead of a cancellation.

If you use a verb instead, you normally do not use の in the same way:

• 予約を取り消すかわりに、日程を変更する。

So the の is there because 予約取消 is a noun-style expression.

予約取消 is a compact noun-style expression meaning reservation cancellation.

It is more formal and more compressed than 予約を取り消す.

Compare:

• 予約取消 = cancellation of a reservation
• 予約を取り消す = to cancel a reservation

Japanese often uses these short noun compounds in formal writing, notices, menus, forms, and customer-service language.

A more conversational version would be:

• 予約を取り消すかわりに、日程を変更する。

Also, in standard writing, you may often see:

• 予約取消し
• 予約の取消し

Those are a little more typical-looking than bare 予約取消, but the given sentence is understandable and has a formal, label-like feel.

日程変更にする means something like:

• make it a schedule/date change
• go with changing the date
• decide on rescheduling

The pattern N にする often means:

• make it N
• choose N
• decide on N

Examples:

• コーヒーにする。
  I’ll have coffee.
• 土曜日にする。
  Let’s make it Saturday.
• 日程変更にする。
  Let’s make it a schedule change / let’s reschedule it.

So this sentence is not just describing a change; it is expressing a choice or decision.

The に is part of the grammar pattern N にする.

This pattern shows the result or option that is chosen.

So:

• 日程変更にする = choose the option of changing the schedule/date
• literally, make it into a schedule change

This is different from:

• 日程を変更する = change the schedule/date

Both can be translated similarly, but the nuance is different:

• 日程変更にする focuses on the decision or option selected
• 日程を変更する focuses on the action itself

Usually yes, in this context it means rescheduling or changing the date/schedule.

But 日程 is a little broader than just one calendar date. It can refer to:

• a date
• a schedule
• planned timing

So 日程変更 can mean:

• changing the date
• changing the schedule
• rescheduling

If you specifically wanted to say just change the date, you might also see:

• 日付変更

But for reservations, appointments, travel, events, and business contexts, 日程変更 is very natural.

Yes. The given sentence sounds compact and somewhat formal, like something you might see in:

• a form
• a service menu
• a business note
• customer support language

A more natural everyday version might be:

• 予約を取り消すかわりに、日程を変更します。
• 予約をキャンセルするかわりに、日程を変えます。

These sound more like normal spoken or written Japanese.

So the original sentence is not wrong, but it is compressed and noun-heavy.

Yes. かわりに is often written as:

• 代わりに

So you may see:

• 予約取消の代わりに、日程変更にする。

In many learning materials, it is written in hiragana as かわりに because that is easier to read.

Both are common.

Yes, it is complete.

Japanese sentences can end in plain-form verbs like する, especially in:

• casual speech
• written notes
• internal thoughts
• neutral statements

So 日程変更にする。 is a full sentence meaning:

• I’ll make it a schedule change.
• Let’s change the date.
• I’ll go with rescheduling.

If you wanted a more polite version, you could say:

• 日程変更にします。

Here are some natural alternatives, depending on style:

• 予約を取り消すかわりに、日程を変更する。
  Instead of canceling the reservation, change the date.

• 予約をキャンセルするかわりに、日程を変更します。
  Instead of canceling the reservation, I’ll change the date.

• 予約取消ではなく、日程変更にする。
  Not a cancellation, but a date change.

• キャンセルせずに、日程変更にする。
  Instead of canceling, make it a date change.

These all express a similar idea, but the original sentence is the most compact and formal-sounding of the group.