Doy el número de servicio al avisar la avería.

Because doy is the conjugated verb form, and dar is just the infinitive.

• dar = to give
• doy = I give

In a normal sentence, Spanish usually needs a conjugated verb. Here the subject is understood as I, so doy is the correct form. Also, dar is irregular in the yo form:

• yo doy
• tú das
• él/ella da

Spanish often leaves out subject pronouns when they are clear from the verb ending.

So:

• Doy already means I give
• Yo doy is also possible, but it adds emphasis

A speaker might say Yo doy el número de servicio... if they want to stress I specifically, but in most cases just doy sounds natural.

Al + infinitive is a very common Spanish structure that often means when doing, upon doing, or while doing something.

So:

• al avisar = when reporting, upon reporting

This structure is made from:

• a + el = al
• plus an infinitive: avisar

It is a compact way to express time. A similar version would be:

• Cuando aviso la avería...

That is a little more explicit, but al avisar is perfectly normal grammar.

Because a + el contracts to al in Spanish.

This contraction is required in almost every case:

• a + el = al
• de + el = del

So al avisar is the correct form, not a el avisar.

Yes, but this is an area where usage can vary by region and style.

In this sentence, avisar la avería means something like report the breakdown/fault. That is understandable, but depending on the country, some speakers may more naturally say:

• avisar de la avería
• reportar la avería
• informar de la avería

So the sentence is grammatical and understandable, but in some parts of Latin America another wording may sound more idiomatic.

Avería usually means a breakdown, fault, malfunction, or service problem, especially with machines, equipment, utilities, or technical systems.

It is often used for things like:

• a car problem
• an appliance malfunction
• a phone/internet/service outage
• a technical fault

In some Latin American regions, learners may also hear words like falla, daño, or descompostura, depending on the context.

Spanish uses articles more often than English does.

Here, la avería refers to the specific fault or breakdown being reported. Even if English might say something like reporting a fault or just reporting the problem, Spanish often prefers the definite article when the situation is understood.

So la avería sounds natural because both speaker and listener know which issue is being discussed.

Spanish usually connects nouns with de where English often puts one noun directly before another.

So:

• service number becomes número de servicio

This is a very common pattern in Spanish:

• tarjeta de crédito = credit card
• centro de salud = health center
• número de teléfono = telephone number

Here, de servicio describes what kind of number it is.

The present tense in Spanish is often used for:

• habitual actions
• general procedures
• instructions
• things that normally happen

So Doy el número de servicio al avisar la avería can describe what the speaker normally does in that situation.

English sometimes uses the present the same way, but Spanish relies on it very naturally for routine actions. If the speaker wanted to emphasize a future action, they could say something like daré, but that would change the tone.

Yes. Spanish word order is flexible, especially with time expressions like al avisar la avería.

For example:

• Doy el número de servicio al avisar la avería.
• Al avisar la avería, doy el número de servicio.

Both are grammatical. The second version puts more focus on the timing or circumstance first. The meaning stays basically the same.

Yes. That is a good alternative.

• al avisar la avería = when reporting the fault
• cuando aviso la avería = when I report the fault

The version with al + infinitive is a little more compact and less personal in feel. The version with cuando is often clearer for learners because it looks more like a full clause.

Both are useful, and both are common structures to know.