Sounds like a split port issue where the routing of your number hasn't updated correctly between the two operators, where either your previous carrier or 48 haven't updated your number routing correctly.
For example, If your previous carrier has your number still listed as theirs because of some error during porting then anyone with that carrier won't be able to contact you until the record gets updated which can be requested by 48.
I had a similar issue a few years ago. Eir eventually did sort it out for me but it is an annoying issue that takes time as it sometimes involves your current carrier having to contact your previous carrier to update their routing of your number.
Eir had me get a phone call or text from three different phone numbers that couldn't contact me, with the SIM in another phone, before they would look into the issue. I had to give them the IMEI of the phone and the phone numbers of the calls and texts so they could look to see what was happening on the system.
Just make sure to keep asking 48 is this a split port issue, is my number being routed correctly.
Is your previous carrier SIM working at all still? Are the phone numbers that are trying to ring and text you from the same carrier? All this info would help when contacting them.
