No assistance

I signed up with Mweb about 3 months ago and I received exceptional service up until now. I am trying to get hold of them for the past week to upgrade my contract however when I call the contact centre I wait for over 20 minutes on the line without anyone answering this happened whole week already I even sent an email to the Sales person that assisted me the first time yet no response. I am seriously upset about this type of service as no one is getting back to me at all and I am thinking about getting a new service provider as I need service and there is no one on the other end to assist me and this is something really troubling to me. If no one gets back to me by next week I am definitely cancelling as I feel should I have a bigger problem then I would not be assisted at all.