Como dizer ''caso queira'' em inglês

I'd like to leave my name and phone number in case you should need my assistance later. (a professional from some tech assistence)
I'll leave my number with in case you need me/in case you need me again/in case you need to contact me. (informal)
Here is my number, in case there's an emergency.
Here's my number, in case you have a chance to call.
Here's my number, if you need further clarifications.

If you feel that the someone else is really going to call you, a new friend, for example:
Please call me on this number.
You can reach me on this number.
You can reach me at 00000-0000.

To more than a phone number turn the word "number" (of above examples) into plural.
And other ways...

In Case Of

• Here, my numbers in case of need.
• I left my numbers, in case of emergency.
• Leave your e-mail address, in case of need.
• In case of doubt, please consult our engineering service.

Bacana! Tinha pensado em "in case", mas achei que "in case you want/wanna" ficaria muito informal. Valeu por esclarecerem!

I see your point! Plus, it leaves open the "don´t want" possibility. And that´s more, "in case you want" is more suitable to give information or to say that some information is available (to everyone, not just to somebody in particular):

Just in case you want see a number you called or review an instant message (IM) you sent ages ago.

In case you want to know better how to move around the city click here.

In case you want to share a room, find a friend to come along with you and enjoy the surf experience together!

Source: Linguee.

Anyway, nobody is going to sue you if you use that way, you would certainly be understood, just that is not the first choice of words of many people.
The "want" there has a certain ring of "if someday you need/when the need arise" or should the need arise...

I understood you, Paulo!

Thank you for the attention and to clear and kind explication!

XO!

I am glad that you liked my explanation!

Recebi um e-mail de um amigo americano que me ofereceu ajuda com a frase: ‘should you find you need assistance, let me know.’ Traduzi como: ‘se você achar que precisa de ajuda, me avise/me diga.’