Account has been closed for no reason & PATHETIC call centre experience,

I've been paying off an account with Nimble for a couple of years, this month I logged into the mobile app and saw the message "You have 0 outstanding accounts with us". I figured this meant that I paid off my account, upon requesting a letter that my account has been paid up via the mobile app, I was informed that my account has not been paid up, but in fact has been closed and sent back to your client (Vodacom).

Why was this done?? I've been paying this account on time every month for years. I just tried phoning your call center three times to sort this issue out, as soon as I mention that my problem is account related, the consultant hangs up, THREE times this has happened in the last 10minutes, SHOCKING experience to say the least, please get into contact with me ASAP as I require some clarity on what the hell is going on here...