Hi Walid, Neither of those is correct. To have the correct tense, ask: when is the speaker talking? Is the day finished or not finished yet? You could say, “My phone was ringing all day” if you mean “yesterday” or “last Tuesday”. But if the person is talking in the afternoon of the same day, use the present perfect: “My phone has been ringing all day.”

I'm ringing,she/he is ringing,you are ringing,we are ringing, they are ringing

The noun is singular. The most natural is, "My phone has been ringing all day."