Vodacom Fibre is pathetic

I took out a fibre line with vodacom a 10 mgps line for 1.5 years and for some reason around august last year they just downgraded my line without my consent, thereafter i experienced terrible speeds but did not think much of it, basically this service that i paid R650.00 per month now became a service for only sending whatsapps, the amount that i was debited changed to R499.00 and i could not download anything, this is **************** and i want a refund from august last year until now and i want my service cancelled immediately, i called a month ago but they still have not cancelled and they had the audacity to charge me for January, i want my money refunded otherwise i am going straight to icasa or the ombudsmen