Need a refund

I have been paying for a 20 mbps Fibre line from October 2017 - April 2018, but only received 4 mbps, after countless emails and phone calls to have it fixed, Vumatel changed a setting. You have been billing me incorrectly for 7 months, I want a full refund for this period. You are not responding on my emails, when will you process my refund???? #KOI- ********** 0 Account number: A ********** 0