^^^ If it only it were that easy.
I do not dispute for one second what the OP says, which is that she was not on the phone. So if that is the case why was a ticket written in the first place?
The answer to that is that it is likely that the police had her under observation for a very short period of time, THINK they saw her on the phone, are not sure but decided to issue a ticket anyway. This does not mean that she was on the phone.
They will (and this is natural and not necessarily a criticism of the police because everyone does it) now convince themselves of what they saw.
Whether the OP was on the phone or not is entirely immaterial. In the absence of any specific direct evidence to the contrary it will be a he said (or they said if there was more than one copper)/she said trial.
It will be then for the Magistrate to decide as a matter of fact whose story they believe to be more credible.
Having said that the CCRs and reverse CCRs will assist the OP greatly in increasing her prospects of acquittal.