Poor arrogant service

Poor arrogant service from mtn: My sister's phone number was hacked and thousands ****** from her bank account (fnb). The bank wants a letter from mtn to proof that her number was hacked and the arrogant mnt is sending my sister from pillar to post. It's been 3 months now. She can't get her money and she also cannot do Sim swap. Can this arrogant company give my sister a simple letter. This is affecting her health. My contact details: ***