Account blocked

I've been with vodacom for 5 years now and have two contracts with them however recently when i try to upgrade my account online as im quite old and unfortunately dont always have the energy and strength to go to the branch however i discover that ********** activity was happening with regard to my account and its flagged and i only can upgrade instore i cant understand how so???i was never informed about this and i am the only person that handles my contracts i am really disappointed as i would like to continue my contract with u guys i am unable to upgrade online??I really do hope my query gets resolved soon and the hold on my account is removed as this is just not on