While you might hear people say "over the phone," it's not grammatically correct. The phrase "on the phone" is more commonly used and accepted.
Here's why:
* "On" implies a state of being. It suggests you are actively using the phone.
* "Over" implies a means of communication. It suggests you are using the phone to communicate with someone.
Here are some examples:
* "I'm on the phone right now."
* "Can we discuss this on the phone?"
* "I talked to her on the phone yesterday."
Hope this helps!