Altec autopage

I have a top up contract with altec autopage. In December my contract was change by them to an open line without my consent or notifying me about any changes. I phoned them to tell them that something is wrong with my contact. So they phoned me today to tell me that I must pay an huge amount or the will suspend my service. I spoke to 3 people and not one knows what is going on on my account. The last person I spoke to was horribly rude to me, screaming and demanding me. <br> Please everyone be aware.