We have a thing when we call a cell phone number that it show it normall so like this: 0496xxxxxx, when the person picks up the number changes to this: +888832496xxxxxx. This happens on the phone that we are using to call. I also checked the logs, the +8888 never shows up in the log files.
Check what SIP profile is assigned to your tunks, I assume is the default profile. You may try two options:
Why does this happen?
If you set “trustrpid=yes” in the definition of the source peer in sip.conf, then Asterisk will copy the number from the RPI header (instead of the From header) of the request is received on the inbound call leg.
According to the above definition, basically means, that when the provider receives the call invite, it adds +8888 on the Remote-Party-ID headers, so, due the trustrpid parameter is enabled, then, the phone shows, what is received on this header, on this case, +888832496xxxxxx.