Can't blacklist a phone because of I don't have the *****s number

So my phone was ****** during a burglary....... I called mtn a couple of days later trying to blacklist my phone.... Now mtn wants the last number that was used on that phone and accoding to my understanding.... The *****s flushed my phone and changed the Sim..... I don't know their numbers(*****s) and mtn can't find the phone on the system even if I give them a IMEI number.... They say they can't link the IMEI with the number I gave them.... Like really.. It's 2021 and you r syterm needs a phone number and IMEI to blacklist..... In the past, you could only blacklist a phone by using IMEI only.... But now you need number as well which common sense would tell you that the number has changed.... So now I lost my phone and I can't even blacklist it..... Very pathetic I must say.....