Rude and unsatisfactory response

My son Asekho Batala passed away on the 05 th of October 2014, he was attacked and hacked to death by ****s in Phillipi Cape Town he was ****** of his cell phone. His cell phone number was *** he was no longer using this number even before his death but when i dial this number i could still here his voice as his voicemail greetings and that is very traumatic. I called MTN customer care center today asking them to shut that line or at least delete the greetings they asked for my number***) and the lady rudely told me that they can not close that line unless i call them from that number despite me telling the lady what happened she also told me that it will automatically close after 90 days which has lapsed already. I don't think the lady who handled my request knows anything about kids let alone losing one, i wish they could just understand my pain and just shut my son's line because it is disturbing my healing process. I can supply them with his death certificate if they want me to or at least allow me to buy a new sim card and sim swap the number at least it would be better if i use it if they can't close it.