Unfortunately, in the documentation we have, there is no information about the command to change the IMEI.
At the same time, we see that the command syntax for your tracker is very similar to the command syntax for Concox trackers. Concox website (https://www.iconcox.com/faq) also states that IMEI is unique and cannot be changed.
Perhaps the command indicated by another user on the forum https://forum.gps-trace.com/d/974-imei-gt06/15 (IMEI,1,00000000000000000#) will help you.
If it does not help, we recommend that you contact the seller or manufacturer of the tracker directly to clarify your issue.
If you get some information, please write about it here, because it can help other users.