Unable to upgrade anywhere

I have been trying to upgrade one of my contract numbers but I keep receiving an error when doing it online. I Then went to a Vodacom store to do it there and try could not assist me and the lady advised me to try and do it online again. I am not the only person experiencing this issue with upgrades, 2 friends have been turned away from a store and told to do it online and the online process gives the same error "There is an problem with a number linked to this account". Please can you assist me with doing an upgrade. This is becoming a hassle now.