[SR-Users] please help with some transformations.

Hi am new to kamilio , but able to make calls, i need to do something really simple if someone can give me an example of it i will be gratefull. just before the call gets relayed i need to delete a prefix from the sip uri so it gets transformed to the same uir but less 3 digits. for example sip:123xxx@domain.com >>> changed to sip:xxxx@dmain.com i tryed with transformations but still too new and does give me so many errors that kamailio don't start, tryed subs_uri but i dont know how to tell it to just take the first tree digits, it is usually done for adding prefixes. please help. thank you in advance. on my scenario i am having an asterisk that i dont control sending me an invite for with a prefix i need kamailio to forward that uri to another server minus the prefix. thank you.