Poor service from Vodacom Business

I purchased a Vodacom business LTE service, returned it within a week due to slowww speed. Since then I have been continued to be billed and there is absolutely no-one who cares enough to help me. The sales person was Felicia Naidoo and I have mailed her and made calls to no avail. Can anyone advise me on who at Vodacom is able to resolve complex issues with customers.