Almost certainly this is number spoofing and there's not much that you or 48 can do about it.
If you want to contact 48 support about this then see the link in my signature below or email them at email@example.com
If your phone is unilaterally making calls then that could be a virus or something similarly nefarious on your phone.
You might want to consider a factory reset of your phone and set it up from scratch.
See my previous reply: