Se houver atraso no voo, a hóspede pode ligar para a recepcionista e mudar a reserva.

Because after se meaning if, Portuguese often uses the future subjunctive when talking about a possible future situation.

• se houver atraso = if there is / if there happens to be a delay
• houver is the future subjunctive form of haver

Compare:

• há atraso = there is a delay (present statement)
• haverá atraso = there will be a delay (simple future statement)
• se houver atraso = if there is a delay (conditional future idea)

So houver is the form the sentence needs.

Here haver means to exist / to be in the sense of there being something.

So:

• haver atraso = for there to be a delay
• se houver atraso = if there is a delay

This is a common formal or neutral way to say that something exists. In everyday speech, many Brazilians would also use ter in similar situations, but haver is very common in more formal written language.

Because no is a contraction:

• em + o = no

So:

• no voo = in the flight / on the flight

Portuguese very often contracts prepositions with articles:

• de + o = do
• de + a = da
• em + o = no
• em + a = na

So em o voo would sound wrong in normal Portuguese; no voo is the correct form.

Because grammatical gender in Portuguese is not determined only by the final letter.

Hóspede can refer to a male or female guest, and the article shows the gender:

• o hóspede = the male guest
• a hóspede = the female guest

So in this sentence, a hóspede tells you the guest is female.

Recepcionista is one of those nouns that often keep the same form for both genders, and the article shows whether the person is male or female:

• o recepcionista = the male receptionist
• a recepcionista = the female receptionist

So the -ista ending does not automatically mean feminine. The article is what tells you the gender here.

Because ligar para means to call someone on the phone in Brazilian Portuguese.

So:

• ligar para a recepcionista = to call the receptionist

This is a very common structure in Brazil. In informal speech, para often becomes pra:

• ligar pra recepcionista

You may also hear telefonar para, which is similar but a bit more formal.

Because after the modal verb pode (can / may), the following verbs stay in the infinitive.

So the structure is:

• pode ligar
• pode mudar

This is similar to English:

• can call
• can change

The conjugated verb is pode, and the verbs that follow it remain in the base form.

Because the same subject, a hóspede, applies to both actions.

The structure is:

• a hóspede pode ligar ... e mudar ...

That means:

• the guest can call
• and the guest can change the reservation

Portuguese often avoids repeating the subject when it is already clear. English does the same:

• The guest can call the receptionist and change the reservation.

You do not need to say the guest twice.

Grammatically, yes: the subject of mudar is still a hóspede.

However, in real-life context, it often means that the guest can make a change to the reservation, probably by contacting the receptionist and requesting the change. So the sentence focuses on the guest’s ability or permission to take that action, not necessarily on who physically updates the system.

Yes, absolutely. That is a very natural alternative.

• Se houver atraso no voo... = If there is a delay in the flight...
• Se o voo atrasar... = If the flight is delayed / If the flight gets delayed...

The original sentence uses the noun atraso (delay) with haver. The alternative uses the verb atrasar (to be delayed / to delay). Both are correct; Se o voo atrasar... often feels a bit more direct and conversational.

Both can be understood, but they are not exactly the same in feel.

• atraso no voo = delay in the flight / a delay affecting the flight
• atraso do voo = the flight’s delay / delay of the flight

In many situations, both would work, but atraso no voo is perfectly natural here and emphasizes the delay occurring in relation to that flight.

Portuguese uses definite articles much more often than English does.

So where English might say:

• the guest
• the receptionist
• the reservation

Portuguese naturally says:

• a hóspede
• a recepcionista
• a reserva

This is very normal. Portuguese often includes articles before professions, roles, and specific nouns where English might sometimes omit them.

It sounds mostly neutral to slightly formal.

Reasons:

• se houver is a somewhat more formal written-style structure
• ligar para is neutral and common
• the overall sentence sounds like hotel or travel-related customer-service language

In more casual everyday Brazilian Portuguese, someone might say something like:

• Se o voo atrasar, a hóspede pode ligar pra recepcionista e mudar a reserva.

That version is more conversational, especially because of atrasar and pra.