Mtn service us so disappointing

My friend received a strange call on the 13th of December after that the phone lost network and the screen displayed an sms that says his number needs a sim swap. He tried to call mtn they he must call after 4 hours, he did that, told to do an affidavit, sent affidavit, following day they say his number has been ported to another network but they not saying which network so ge needs to do another affidavit saying he needs his number back. It's so disappointing shame service from mtn, i mean jow do you let the number to be ported without the owner's consent? And he has been using this number since forever.