To have a phone conversation in Engpsh, you can say: "Can we have a phone conversation in Engpsh?" or "Can we speak on the phone in Engpsh?" If you are already on the phone with someone and you want to switch to speaking in Engpsh, you can say: "Can we switch to speaking in Engpsh?" or "Can we continue this conversation in Engpsh?" It's also common to simply say "Hello" when answering the phone and then introduce yourself and state the purpose of your call. For example: "Hello, this is John. May I speak to Sarah, please?"