seikyuusyo no kingaku ga sukosi tigatte ita node, kaisya ni kikimasita.

Here, の links two nouns and works a bit like of in English.

• 請求書 = invoice, bill
• 金額 = amount, total amount

So 請求書 の 金額 means the amount on the invoice or the invoice amount.

This is a very common noun-modifying pattern in Japanese:

• 日本の会社 = a Japanese company
• 本の名前 = the name of the book

In this sentence, 請求書 の 金額 is the thing being talked about.

Because 違う is not used with a direct object here. It describes something as being different.

So:

• 金額 が 違う = the amount is different

The particle が marks 金額 as the subject of 違う.

Using を would sound wrong here. Japanese treats 違う as describing the state of the amount, not as an action done to it.

少し means a little or slightly.

So:

• 少し違っていた = was a little different

It comes before the verb phrase because adverbs in Japanese usually come before what they modify.

Compare:

• 少し高い = a little expensive
• 少し分かります = I understand a little

Here it softens the statement, suggesting the amount was not completely wrong, just somewhat off.

The dictionary form is 違う, which means to differ or to be different.

The form 違っていた breaks down like this:

• 違う
• 違って = て-form
• いた = past of いる

Together, 違っていた means something like was different or had been different.

Both can be translated as was different, but the nuance is a little different.

• 違った = simply states that it was different
• 違っていた = describes the amount as being in the state of being different at that time

In many situations, 違っていた sounds more natural when noticing a condition or situation that existed.

So here, 請求書の金額が少し違っていた suggests:

• the invoice amount turned out to be different
• when the speaker checked it, it was in that state

This ている / ていた pattern is often used for states or resulting conditions, not only ongoing actions.

Both ので and から can mean because, but ので usually sounds a bit softer and more explanatory.

• ので = because, since; often gentler and more neutral
• から = because; often more direct or personal

So:

• 違っていたので、会社に聞きました = Because it was different, I asked the company.

Using ので fits well in a situation like explaining why you contacted a company. It sounds calm and matter-of-fact.

The comma marks a pause between the reason part and the main action.

• 請求書の金額が少し違っていたので = because the amount on the invoice was a little different
• 会社に聞きました = I asked the company

Japanese commas are often used more flexibly than English commas, but here it helps separate the cause from the result.

With 聞く, the particle に is often used for the person or organization you ask.

• 先生に聞く = ask the teacher
• 会社に聞く = ask the company

So に marks the target of the question.

You may also see 会社へ問い合わせました in more formal business Japanese, but 会社に聞きました is a straightforward everyday way to say it.

It can mean either, depending on context.

聞く has several related meanings:

• to hear
• to listen
• to ask

In this sentence, because it is 会社に聞きました, it clearly means asked the company.

Examples:

• 音楽を聞く = listen to music
• 話を聞く = hear/listen to a story
• 先生に聞く = ask the teacher

So the particle and context tell you which meaning is intended.

会社 simply means company, and from context it is understood to mean the company that sent the invoice.

Japanese often leaves out details that are obvious from context. So instead of saying:

• 請求書を送った会社に聞きました

it is natural to shorten it to:

• 会社に聞きました

If the context is clear, Japanese prefers the simpler version.

Japanese often omits the subject when it is clear from context.

Here, 聞きました tells us someone asked the company, and in normal conversation or writing it is easy to understand that it was the speaker.

So the sentence naturally implies:

• 私は会社に聞きました = I asked the company

But saying 私は is not necessary unless you want emphasis or contrast.

The main verb is 聞きました, which is past tense, so the sentence as a whole is talking about a past action:

• I asked the company

The reason clause is also in the past:

• 違っていた = was different

So the full sequence is:

1. the amount was a little different
2. because of that, the speaker asked the company

Yes, 請求書の金額が少し違いましたので、会社に聞きました is possible and understandable.

However, 違っていた can sound a little more natural when describing a situation the speaker noticed and then reacted to. It gives the sense that the amount was in a differing state when checked.

So:

• 違いました = it was different
• 違っていました / 違っていた = it had been different / it was in a different state

The difference is subtle, and both could appear in real Japanese.

The basic meaning would stay the same as long as the particles remain correct, but the original order is the most natural.

Standard order here is:

• topic or item being described
• reason
• main action

So:

• 請求書の金額が少し違っていたので、会社に聞きました。

Japanese word order is more flexible than English, but the reason clause usually comes before the main clause when using ので.

For example, you could say:

• 会社に、請求書の金額が少し違っていたので、聞きました。

But this sounds less natural than the original.

No, they are different.

• 請求書 = invoice, bill
  A document asking for payment
• 領収書 = receipt
  A document showing that payment was received

So in this sentence, 請求書 is correct because the speaker is checking the billed amount, not a receipt after payment.

In some business contexts, yes.

• 聞きました = asked
• 問い合わせました = made an inquiry, contacted to ask

So:

• 会社に聞きました sounds simple and everyday
• 会社に問い合わせました sounds more formal and business-like

If this is casual explanation, 聞きました is perfectly fine. If it is in formal office Japanese, 問い合わせました may sound more polished.