We recently upgraded to 40Mbps VDSL, and after the upgrade the line synced at 40Mbps. It worked using the Telkom guest account, but it would not authenticate another ISP account which means that it did not connect to the Internet.
The cause: After a VDSL upgrade you have to verify your account here: https://secureapp.telkom.co.za/ADSLVERIFY_NEW/verifyRequest.do#.U8QxbfmSyOQ
You can also call 10210 and ask the helpdesk operator to verify your new service.
After this was done you will be able to use any ISP account, and it will authenticate.
I hope this helps.
The cause: After a VDSL upgrade you have to verify your account here: https://secureapp.telkom.co.za/ADSLVERIFY_NEW/verifyRequest.do#.U8QxbfmSyOQ
You can also call 10210 and ask the helpdesk operator to verify your new service.
After this was done you will be able to use any ISP account, and it will authenticate.
I hope this helps.