Mtn vultures

Mtn call center called my 70 year old dad selling him some product, we don't know if it's a phone or modem. I have tried calling their 135 numbers and the other numbers on any website I could find to cancel this delivery. I even called Uti Mounties who are the courrier that called my dad to deliver the product they told me I need to contact mtn. I have sent messages on Facebook which they responded to. They said my dad needs to contact them but we can't get hold of anyone so I have asked them to call him and given them his number. I'm not sure what else I can do. I will continue to contact via social media but other help would be appreciated.