refuse to pay my refund

I have been dealing with the most disgusting service ever...I have been trying to cancel my service with telkom due to their pathetic service with regards to my internet line for more than 6 months have they failed to cancel my service but they over billed me as well a refund was due to me 5 months ago and still they refuse to pay me back my money...I thought telkom is 1 of the best service providers but after this I will never recommend telecom to any 1 untill my issue is resolved and if it's not resolved soon I'll be taking it to court...