“why don't I/ I don't/ have your phone number” vs "why I am not / am I not/ having your phone number

Question

Suppose you work in a office and there is a guy there who you know for a year and you he asks you to call him so that he could find his missing phone through hearing the phone vibrating or something. The point however is, you don't have him as a contact on your phone and you want to say that in a kind of funny way, you don't have his number like below:

• why I don't have your phone number?
• why I am not having your phone number?
• why am I not having your phone number?
• why don't I have your phone number"?

Would please tell me if those are idiomatic questions considering the context? And is there any difference between the different interrogative constructions above in general?

Answer 1

We don't use to have in a progressive sense when it means to possess: we say I have your phone number, not I am having your phone number. So any version with the progressive is wrong:

• Why I don't have your phone number?
• Why I am not having your phone number?
• Why am I not having your phone number?
• Why don't I have your phone number?

Also, when we make wh- questions in English, we change the word order: the wh- word, like Why, is immediately followed by the auxiliary verb do, then the subject, then the main verb. So the proper order is Why don't I have... and that leaves us with only one choice:

• Why I don't have your phone number?
• Why don't I have your phone number?

That's the only idiomatic, grammatically correct way to say the question.

Answer 2

Your second and third sentences are incorrect. In English the present continuous is not used in this case. The first and fourth sentences are using the correct tenses but I have doubts about the questions that you are asking..

The first question,:

Why I don't know your number?

effectively means, 'Why are you asking me to call you. I don't have your number'. From the context of your prelude, I doubt if this is what you meant to say.

The fourth question,:

Why don't I have your phone number?

effectively means, 'I don't have your number. Why don't I have it?'. Again, from the context of your prelude, I doubt if this is what you meant to ask.

It may be better to respond along the following lines:

I would really love to help, but I don't have your number in my phone.

or

I'm sorry, I don't have your number in my phone. But I am happy to call you if you give me your number.