avanza1807 Hello!
Have you forgotten the phone number of the SIM card or chip that you use with your tracker?
If this is the case, then the easiest option is to check the number with your communication operator or through your payment data, for example, when you paid for communication services. Also, if you set up the tracker via SMS commands, then probably there should be an SMS history on your phone, in which you can see to which number you sent SMS with commands.
As a rule, trackers do not send in messages the phone number they are using.