Looking on the internet deeply has found these results:

can I call you? is the most popular phrase on the web.

Could I call you? 1898,000 results on the web	can I call you? 14,800,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
Well, I'm cutting out of here early today... and doing a little duck hunting... but maybe I could call you tonight? Mr. McNaughton, is there someone I could call for you? Later? Could I call you? In my letters, could I call you "Brother"? Do you think you could call me James and I could call you Amelia? Nikolai, could I call you back? Ms. Detroit, could I call you Alice? The last thing I want to do is upset this investigation, but if I have any more feelings about the case, could I call you?	Hello? Can I call you back? What can I call you? Sir Lawrence... can I call you Larry? Can I call you Victoria? No. How can I call you? Can I call you back? I'm... going into a tunnel. But how can I call you? Sofia, can I call you?

Could I call you?

1898,000 results on the web

can I call you?

14,800,000 results on the web

More popular!

Well, I'm cutting out of here early today... and doing a little duck hunting... but maybe I could call you tonight?
Mr. McNaughton, is there someone I could call for you?
Later? Could I call you?
In my letters, could I call you "Brother"?
Do you think you could call me James and I could call you Amelia?
Nikolai, could I call you back?
Ms. Detroit, could I call you Alice?
The last thing I want to do is upset this investigation, but if I have any more feelings about the case, could I call you?