Line keeps getting suspended and no one can explain why

I upgraded my data contract at the end of 2015, and that is when the problems started. I keep getting disconnected for exceeding caps/limits. My old contract had 5GB "free" and there were never any issues; the new one has 5GB anytime plus 5GB night-time, and I use wi-fi at work, yet according to MTN, I keep hitting some sort of cap, although no one can really explain it. I started keeping a record of the past few months (below). As I write this, I have not had a connection since the morning of 27 April (that's nearly 3 days now) and no one has called back since my last conversation with the call centre. Can someone please tell me what the heck is going on and get this fixed once and for all? I have been an MTN customer for a very long time and you will notice that your debit orders go off without a hitch every month, so how about some service in return? 25 Feb 2016: Went to branch, was told connection would be back in 30 minutes. They also took a copy of my ID and sent a mail to someone to remove caps on my account. When connection did not come back after 2 hours, called the call centre, and they finally managed to restore everything, ref no *** 13 Mar 2016: Called call centre at 10:10am, 10:15am (both dropped after 3 mins on hold without speaking to agent). 10:23am was promised that the connection would be back after I restart the device, ref no ***. After a while, still no connection, called 11:46am (dropped), 11:50am turns out line was still suspended, connection restored, ref no *** 23 April 2016: 8:14am Spoke to call centre, connection restored, ref no *** 27 April 2016: Not connecting all day, 7:15pm called the call centre. Lady could not tell me what limit I exceeded (as per usual) nor could she unlock the line (the option was "greyed out" in her system), but she sent a mail to someone who might be able to help. Call dropped before I could get a reference number.