Monthly overcharge and poor service to rectify invoices

RSA Web is continuously billing me incorrectly irrespective of sending them proof of the promo package purchased. As well as snippets of the conversation between myself and a consultant at the time or placing the order. They take forever to correct the invoices and send threats of cutting your Fibre line whilst in dispute because of crediting your invoice. Can you not just give me the right invoice to pay so that my life can go on? Tiring to go through this every month!!!