El servei d'atenció al client obre avui.

Because de becomes d' before a word that begins with a vowel. This is very common in Catalan.

• de + atenció → d'atenció

It works much like elision in French. So servei d'atenció literally means something like service of assistance/attention.

Al is a contraction of a + el.

• a = to / for
• el = the
• al = to the / for the

So:

• atenció al client = attention/service for the customer

This contraction is very common in Catalan, just like:

• del = de + el

Catalan often uses the singular in expressions where English may use a more general noun, especially in set phrases.

So atenció al client is a standard expression meaning customer service or service for customers in general. It does not mean only one specific customer is being helped.

You could also find plural forms in other contexts, but atenció al client is the usual fixed phrase.

Obre is the third person singular present tense of the verb obrir (to open).

So:

• jo obro = I open
• tu obres = you open
• ell/ella obre = he/she/it opens

Here, the subject is El servei d'atenció al client, which is singular, so the verb must also be singular:

• El servei ... obre = The service ... opens / is open

It can often be understood as opens today, but in real usage it may also imply is opening today or will open today, depending on context.

Catalan present tense is often used where English might use:

• simple present: opens
• present progressive: is opening
• sometimes even near-future: opens today / will open today

So the exact English wording depends on the situation, but the Catalan form obre is completely natural here.

Yes, very much so. It is a standard way to say customer service.

Literally, the parts are:

• servei = service
• d'atenció = of assistance/attention
• al client = to the customer

But as a whole, it functions like one unit meaning customer service department, customer support, or customer service depending on context.

Yes. Avui means today, and Catalan allows some flexibility with adverb placement.

You can say:

• El servei d'atenció al client obre avui.
• Avui obre el servei d'atenció al client.

Both are grammatical, but the emphasis changes slightly.

• ... obre avui puts the time information at the end.
• Avui obre ... emphasizes today more strongly.

The version you were given is neutral and natural.

Because servei is a masculine singular noun in Catalan.

So it takes:

• el = masculine singular the

Not:

• la = feminine singular the

This is something learners just have to memorize with the noun:

• el servei
• el client
• l'atenció is actually feminine, but because it begins with a vowel, la becomes l'

There could be one in other contexts, but in this expression Catalan normally uses servei d'atenció al client without it.

That is because d'atenció al client works as a complement describing what kind of service it is. In English, we also often do this without an article in compound expressions, as in customer service rather than service of the customer attention.

So here the most natural form is:

• servei d'atenció al client

not usually:

• servei de l'atenció al client

A simple learner-friendly pronunciation guide would be:

el ser-VEI da-ten-see-O al klee-ENT O-breh uh-VUI

A few useful notes:

• servei has stress on the last syllable: ser-VEI
• atenció has stress on the final syllable: ten-see-O
• client is usually pronounced as two syllables: klee-ENT
• avui is stressed on the second syllable: uh-VUI

Pronunciation varies somewhat by dialect, but this will guide you well.

You might be understood, but it is less standard if you specifically mean customer service as a department or service desk.

The usual expression is:

• servei d'atenció al client

This is the idiomatic way to refer to customer service.
Servei al client can appear in some contexts, but it does not sound as fixed or as standard for this meaning.