Si no recibo respuesta hoy, voy a reclamar en la oficina.

Because after si for a real or possible future condition, Spanish normally uses the present tense, not the future.

So the pattern is:

si + present, future/result

In this sentence:

• si no recibo respuesta hoy = if I don’t receive a reply today
• voy a reclamar en la oficina = I’m going to complain / make a claim at the office

Using si no recibiré would sound wrong in standard Spanish.

Both are possible, but they give slightly different feels.

• voy a reclamar sounds a bit more immediate, planned, and conversational
• reclamaré sounds a bit more formal or definite

So:

• Si no recibo respuesta hoy, voy a reclamar en la oficina.
• Si no recibo respuesta hoy, reclamaré en la oficina.

Both are correct. In everyday speech, ir a + infinitive is very common.

Here, reclamar means something like:

• to complain
• to file a complaint
• to make a claim
• to demand what is due

In Spain, reclamar is often used in customer-service or administrative situations. It can sound stronger and more formal than just quejarse.

So this is not just casual complaining. It suggests taking action at an office, desk, or institution.

Spanish often leaves out the article when speaking in a general sense.

So recibo respuesta means I receive a reply / any reply.

If you say recibo una respuesta, that sounds a little more specific, as if you are referring to one reply as a countable item.

In many contexts, both are possible, but recibir respuesta is a very natural expression in Spanish.

Because the speaker is talking about receiving a reply in a general sense, not multiple replies.

recibir respuesta is a common fixed-type expression meaning to get a response.

If you used the plural, recibir respuestas, it would suggest multiple answers, which is less likely in this context.

Because Spanish usually leaves out subject pronouns when the verb ending already shows who the subject is.

• recibo = I receive
• voy = I go / I am going

So yo is unnecessary unless you want emphasis or contrast.

For example:

• Si no recibo respuesta hoy, voy a reclamar... = neutral
• Si no recibo respuesta hoy, yo voy a reclamar... = more emphatic, maybe contrasting with someone else

Because en la oficina tells you where the complaint will happen.

• reclamar en la oficina = to complain / file a claim at the office

If you said a la oficina, that would suggest movement to the office.

Compare:

• Voy a reclamar en la oficina. = I’m going to complain at the office.
• Voy a la oficina a reclamar. = I’m going to the office to complain.

Both are possible, but they mean slightly different things.

Yes. That is also correct.

Compare:

• Si no recibo respuesta hoy...
• Si hoy no recibo respuesta...

Both mean the same basic thing: If I don’t receive a reply today...

The difference is just emphasis and rhythm:

• Si no recibo respuesta hoy puts today a little later
• Si hoy no recibo respuesta brings today forward for emphasis

In Spanish, no normally goes directly before the conjugated verb.

So:

• no recibo = I do not receive
• no voy = I am not going

That is the normal word order.

Here:

• si no recibo respuesta hoy = if I don’t receive a reply today

Yes, in this sentence the comma is standard and natural.

When a conditional clause comes first, Spanish usually separates it from the main clause with a comma:

• Si no recibo respuesta hoy, voy a reclamar en la oficina.

If the main clause came first, the comma is usually not used:

• Voy a reclamar en la oficina si no recibo respuesta hoy.

So the comma helps mark the boundary between the condition and the result.

It is a real or open condition.

The speaker sees this as a real possibility:

• If I don’t get a reply today, I’m going to complain.

That is why Spanish uses:

• si + present
• then a future-type result such as voy a reclamar

A more hypothetical or unlikely condition would use a different structure, for example:

• Si no recibiera respuesta hoy, reclamaría...

But that is not what this sentence is doing.

Yes, but the tone changes.

• respuesta is the most neutral and common choice
• contestación can sound a bit more formal or administrative in some contexts
• respuesta alguna means any reply at all and adds emphasis, often sounding more formal or more forceful

Examples:

• Si no recibo respuesta hoy... = neutral, natural
• Si no recibo contestación hoy... = slightly more formal
• Si no recibo respuesta alguna hoy... = more emphatic/formal

So the original sentence sounds very natural and everyday.