zhè jiùshì kèfúdiànhuà.

In this sentence, 这 works as a pronoun meaning this.

So:

• 这就是客服电话。 = This is the customer service phone number.

You do not need 个 here, because 这 is not directly modifying a noun right after it. It is standing alone as this.

Compare:

• 这是客服电话。 = This is the customer service phone number.
• 这个电话是客服电话。 = This phone is the customer service phone number/line.

A simple way to think about it:

• 这 = this as a standalone pronoun
• 这个 + noun = this + noun

Both 这 and 这个 can sometimes appear in speech, but 这就是... is very natural here.

就是 is 就 + 是.

Here, 是 is the basic verb to be, and 就 adds emphasis. In this sentence, 就是 gives a sense like:

• this is exactly...
• this is in fact...
• this is the very...

So the difference is roughly:

• 这是客服电话。 = This is the customer service phone number.
• 这就是客服电话。 = This is the customer service phone number. / This is exactly the customer service number.

The English translation may look almost the same, but 就是 often sounds more definite, confirming, or identifying something clearly.

For example, it can be used when:

• you have finally found the number
• you are correcting someone
• you are pointing out the correct one

客服 is short for 客户服务, which means customer service.

So:

• 客户 = customer
• 服务 = service
• 客服 = customer service (shortened form, very common)

In modern Mandarin, shortened forms like this are extremely common, especially in everyday speech, business, and online language.

So 客服电话 literally means something like:

• customer-service telephone
• more naturally: customer service phone number or customer service line

It is best understood as a compound noun:

• 客服
  • 电话

Together they mean customer service phone / customer service phone number / customer service line.

Chinese often builds nouns by putting words together without extra connectors like of, for, or 's.

So instead of saying something literally like telephone for customer service, Chinese simply stacks the nouns:

• 客服电话

This is very normal in Mandarin.

Because 客服电话 is a tight noun compound, and Chinese often leaves out 的 in this kind of fixed expression.

Compare the pattern:

• 客服电话 = customer service phone
• 公司电话 = company phone
• 学校老师 = school teacher
• 中文老师 = Chinese teacher

If you inserted 的, it would sound less like a fixed compound and more like a looser descriptive phrase:

• 客服的电话 usually means customer service's phone or the phone belonging to customer service

That is a different nuance.

So in 客服电话, no 的 is needed.

It can mean different things depending on context.

电话 commonly means:

• telephone
• phone call
• sometimes phone number / phone line, especially in practical expressions

In 客服电话, it usually refers to the customer service phone number or customer service line, not just the physical telephone device.

Chinese often relies on context more than English does.

If someone wanted to be more explicit, they might say:

• 客服电话号码 = customer service phone number

But 客服电话 is already very natural and common.

The pinyin is:

• 这 zhè
• 就是 jiùshì
• 客服电话 kèfú diànhuà

Full pronunciation:

• zhè jiùshì kèfú diànhuà

Tone by tone:

• 这 = 4th tone
• 就 = 4th tone
• 是 = 4th tone
• 客 = 4th tone
• 服 = 2nd tone
• 电 = 4th tone
• 话 = 4th tone

A natural rhythm is:

• 这｜就是｜客服电话。

Because there are many 4th tones in a row, native speech may sound a little less sharply separated than a textbook reading. But the dictionary tones stay the same.

Yes, it is natural.

It sounds especially natural when someone is:

• identifying the correct number
• pointing something out
• confirming information

For example, if someone asks which number to call, you could point at one and say:

• 这就是客服电话。

If you want a more neutral statement, you can also say:

• 这是客服电话。

That version is slightly plainer and less emphatic.

The core meaning is the same, but the feeling is different.

这是客服电话

• simple statement
• neutral
• just giving information

这就是客服电话

• more emphatic
• sounds like this is the one
• often used for confirmation, clarification, or emphasis

So if you are simply labeling something, 这是客服电话 is fine.

If you are saying this is exactly the customer service number you need, then 这就是客服电话 fits better.

Yes.

You can say:

• 这是客服电话吗？
• 这就是客服电话吗？

Both are correct.

The difference is similar to the statement versions:

• 这是客服电话吗？ = Is this the customer service phone number?
• 这就是客服电话吗？ = Is this the customer service phone number, then? / Is this the exact customer service number?

The version with 就是 can sound a bit more like checking whether this is the exact one.

Mandarin does not have articles like English a, an, and the.

So Chinese can simply say:

• 这就是客服电话。

and the listener understands from context whether it means:

• the customer service phone number
• a customer service phone number
• the customer service line

Context does the job that articles often do in English.

This is one reason Chinese sentences can look shorter than English ones.