Poor service from call centre

I am shocked at the way Telkom's customer call centre handles their customers.I am trying to upgrade my internet account,as I am constantly running out of data,so I asked them to call me back.Someone did call,and when I said what I want to do,she slammed the phone in my ear.Unfortunately there are no other service providers in my area,otherwise I would have moved already.The customer portal is so slow,it takes ages to do a top-up.