Learn Italian: C'è un incendio: chiamo subito i soccorsi. - There is a fire: I immediately call for help.

You would use the present tense of stare + per + the infinitive verb. So, "I am about to call" becomes sto per chiamare. In this sentence, the speaker instead uses chiamo subito (I call immediately) because they are taking action in this exact moment, rather than just getting ready to act.

Why is "help" translated as the plural i soccorsi?

In Italian, when you refer to emergency services, rescue workers, or help in a crisis, it is usually pluralized as i soccorsi (literally "the rescues"). If you used the singular il soccorso, it would refer more to the abstract concept of help or first aid (pronto soccorso).

Could I use the future tense instead of the present tense chiamo here?

You could say chiamerò (I will call), but Italians frequently use the present tense for actions happening in the immediate future. Because the action is happening right now (subito), the present tense chiamo feels much more urgent and natural.

Why does the adverb subito go directly after the verb?

Adverbs of time, like subito (immediately or right away), typically follow the verb they modify in Italian. While you could also place it at the end of the sentence (chiamo i soccorsi subito), placing it right after the verb is the most standard word order.