I shall talk to you _____ telephone.

The phrase "over the phone" means that something is done using the phone as a way to do it. The following examples show how "over the phone" is used:

• She told him the news over the phone. [=she used the phone to tell him the news rather than telling him in a letter or in person]
• I am able to pay my bills over the phone so I don’t have to write checks.
• We ordered take-out over the phone before driving to the restaurant to pick it up.