أتصل حالا.

In careful MSA pronunciation, it is:

أَتَّصِلُ حالًا
attaṣilu ḥālan

A few useful notes:

• أتصل is usually pronounced attaṣilu, with a doubled t sound.
• That doubling comes from the hidden shadda on ت.
• حالا is more fully written حالًا in fully vocalized Arabic.

So the sentence is not pronounced letter-by-letter as a-ta-si-lu; it is at-ta-ṣi-lu.

أتصل is the 1st person singular imperfect form of the verb اتصل.

That means it can mean:

• I call
• I am calling
• I will call

The exact English translation depends on context. In this sentence, because of حالا meaning immediately/right away, it often comes across as:

• I’ll call right away
• I’m calling right now

Because Arabic verbs usually already show the subject.

In أتصل, the prefix أَ- tells you the subject is I. So Arabic does not need أنا here.

• أتصل = I call / I am calling / I will call
• أنا أتصل = I call with extra emphasis on I

So the short sentence is completely normal.

In Arabic, the imperfect verb can express the present or the future, depending on context.

Here, حالا gives the idea of immediately / right away, so the sentence often sounds like a near-future promise or intention:

• I’ll call right away

If you want to make the future more explicit, Arabic could also say:

• سأتصل حالًا = I will call right away

But أتصل حالا is still understandable and natural in context.

حالا means immediately, right away, or at once.

It functions like an adverb in English. In fully vocalized Arabic, it is usually written:

حالًا

So in this sentence it tells you when the calling happens:

• أتصل حالا = I’ll call immediately

Because the fully vocalized form usually has tanwīn fatḥ at the end:

• حالًا

In everyday Arabic writing, short vowels and tanwīn are often omitted, so you may see:

• حالا

Both point to the same word here. For learners, it is useful to know that the full formal spelling with case ending is حالًا.

Not exactly.

• الآن = now
• حالًا = immediately / right away

Sometimes they overlap in English translation, but the feeling is different:

• أتصل الآن = I’m calling now
• أتصل حالًا = I’ll call right away / immediately

So حالًا often adds a sense of promptness or urgency.

The hamza in أَتَّصِلُ is part of the 1st person imperfect prefix أَ-, which marks I.

This is different from the past tense اتصل:

• اتصل = he contacted / called or ittaṣala in the past form
• أتصل = I contact / call in the imperfect

So the hamza helps distinguish the verb form.

Because this verb belongs to a derived pattern in Arabic, and in this form the ت is pronounced with shadda:

أَتَّصِلُ

So you say:

• at-ta-ṣi-lu

not:

• a-ta-ṣi-lu

This doubled consonant is an important part of the word’s correct pronunciation.

Not only that.

In Modern Standard Arabic, اتصل often means:

• to call
• to contact
• to get in touch

In modern everyday usage, it is very often used for phone calls, but the meaning can be broader than just telephoning.

Not necessarily. The sentence can stand alone if the person being contacted is understood from context.

But very often Arabic adds بـ before the person:

• أتصل بك = I’ll call you
• أتصل به = I’ll call him / contact him
• أتصل بها = I’ll call her / contact her

So أتصل حالا is fine as a short sentence, but it leaves the object understood.

Yes, it is understandable as MSA, but a fully vocalized textbook-style version would usually be:

أَتَّصِلُ حالًا

Things often omitted in normal writing are:

• the shadda on ت
• the final short vowel on أتصل
• the tanwīn on حالًا

So the written sentence أتصل حالا. is a common unvocalized version of the more fully marked form.