deetayouryou, roominguryoukin, opusyonsaabisu wo kakuninsuru.

Because all three nouns are the direct objects of the same verb, Japanese usually puts を only once after the whole list.

So:

• データ容量
• ローミング料金
• オプションサービス

are all being acted on by 確認する.

This is more natural than repeating を after every item.

を marks the direct object of the verb.

Here, the verb is 確認する meaning to check / confirm, so を shows what is being checked.

In this sentence, the things being checked are:

• データ容量
• ローミング料金
• オプションサービス

Japanese often uses 、 to list items without adding a separate word for and.

So データ容量、ローミング料金、オプションサービス is simply a list:

• data allowance/data capacity
• roaming charges
• optional services

This style is very common in menus, instructions, labels, and short written statements.

You could also connect nouns in other ways, such as with と, but a comma list is very natural here.

Japanese is basically an SOV language: subject-object-verb.

That means the verb usually comes at the end of the sentence or clause.

So the structure here is:

• objects: データ容量、ローミング料金、オプションサービスを
• verb: 確認する

This word order is completely normal in Japanese.

Yes, it functions as a verb meaning to check, to confirm, or to verify.

Grammatically, it is a suru-verb:

• 確認 = confirmation/check
• する = to do

Together, 確認する means to do a check or more naturally to check.

This is a very common pattern in Japanese:

• 勉強する = to study
• 予約する = to reserve
• 確認する = to confirm/check

確認する is the plain/dictionary form.

You often see the dictionary form in:

• headings
• menu items
• button descriptions
• instruction lists
• manuals
• neutral written style

If this were a polite spoken sentence, it could become 確認します.

For example:

• データ容量、ローミング料金、オプションサービスを確認します。

But in a UI or a written instruction, 確認する is very natural.

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

In a sentence like this, especially in an app, website, or instruction manual, the subject is unnecessary. Depending on context, it could mean:

• Check ...
• You can check ...
• To check ...
• Checking ...

Japanese frequently omits information that English usually states directly.

It is grammatically a sentence in dictionary form, but in real life it often feels more like a label, command heading, or function name.

For example, you might see this on:

• a phone carrier website
• an app screen
• a support page
• a list of available actions

So rather than sounding like everyday conversation, it has a practical, written, interface-style feel.

Two of them are clearly loanword-style expressions, and the sentence as a whole uses a lot of modern service-related vocabulary.

• データ = data
• ローミング = roaming
• オプションサービス = option service / optional service

These are written in katakana, which is commonly used for:

• foreign loanwords
• technical terms
• brand-like terms
• modern business/service vocabulary

容量 and 料金 are not loanwords, though:

• 容量 = capacity/amount
• 料金 = fee/charge

So some parts are katakana loanwords, and some parts are standard Japanese words.

Literally, yes: データ容量 means data capacity/amount of data.

In real-world usage, especially with phones or mobile plans, it usually means something like:

• data allowance
• available data amount
• data usage limit

So it refers to how much mobile data is included, available, or being used, depending on context.

Yes, but the nuance and style would change.

For example:

• データ容量とローミング料金とオプションサービスを確認する。

This is grammatical, but it sounds less natural for a neat written list like this.

Using 、 is cleaner and more common in headings or interface text.

Also, if you use と, it often emphasizes a complete A and B and C list in a more sentence-like way, while commas are very natural for compact listing.

It is best thought of as neutral written style rather than casual conversation.

• 確認する is plain form
• but the vocabulary is formal/practical
• the overall tone sounds like UI text, documentation, or a service guide

So it is not especially casual, even though it is not in polite -ます form.

A few natural possibilities are:

• データ容量、ローミング料金、オプションサービスを確認してください。
  = Please check your data allowance, roaming charges, and optional services.

• データ容量、ローミング料金、オプションサービスを確認できます。
  = You can check your data allowance, roaming charges, and optional services.

• データ容量、ローミング料金、オプションサービスを確認します。
  = I/we will check the data allowance, roaming charges, and optional services.
  or in some contexts, a polite statement of action.

The original 確認する is more like the base form used for a heading or action name.