Unable to make calls on MTN, 100Gigs finished in 6 days???

Hello, I'm unable to make calls from my MTN number. I have restarted my phone, removed the sim and waited. This is frustrating as I have airtime but cannot use it. I pay on time monthly for this contract but am not getting good service from this Network.

It is highly inconvenient especially because I cannot speak to an operator at the call center, all I get is self help options which don't help with this issue.

Secondly, within 6 days, 100 gigs of data got used. I have no idea what could have used so much of data. I am now unable to use my wifi as above and unable to make calls. I am truly disappointed. Please assist me.

Regards,