Personally I feel that you should not have to contact the call centre for 90% of the reasons. I always use the call centre as the last resort after having exhausted all other opportunities.
Unfortunately Sentech's website is one of the worst. Their coverage map is broken and has been broken for over a month. It is impossible to create a new account to see if your area is covered. Eventually you have to phone them. We opted for the R99pm Mywireless Lite package of which Nowire is the reseller. Unfortunately what they did not point out was that whenever you try to do anything they will always blame the other partner. Nowire are not available on Sundays, and are only available on Saturday's up to 13h00. Typically, the first time we ran out of bandwidth was on a Sunday. Try as we may it was impossible to even get hold of a Nowire person, and phoning Sentech was fruitless as the Nowire accounts are apparently hidden from Sentech, and as such we could not buy any additional bandwidth come hell or high water. On Monday we tried to order some more bandwidth again and even though we have more than R100 of credit on our nowire account we could not simply buy bandwidth and it was required that we send through a fax requesting that we need additional bandwidth. This was so unbelievable that we opted to wait out the last week of the month so that we could get more data again on the beginning of the next month. A disgusting business practice for an Internet Service provider. Then in the next month we tried to see how much bandwidth we had left on the account. Unfortunately the sentech website could not provide us with the details because that feature was broken. A phonecall to Sentech was just as fruitless because the operator said that the feature is broken so he can't access it either. A week later, and nothing has been done to fix the problem.