Just cut you off after you've paid

I made arrangements to pay this month some of the areas of last month, I paid today R600 in their account and contacted them via chat on their website earlier and spoke to Moneeba who couldn't get hold of whatever department, in the meantime they cut our internet off!! I'm canceling with them and they must pay my R600 back and I'll find another service provider because I've been with them for years but just cut us off when the payment goes directly into their account that they get immediately!