CELL C Debit order change from abroad.

I need to change my debit order bank account from whilst working abroad. Cell C will only do this by phoning you on your number which is not possible as they never activated roaming inspite of doing it by phone and going to the Cresta branch to confirm who confirmed roaming can only be done by phone. Ive tried emailing but just got no-where. This blank wall of doing it by phone. So out of frustration reported this on Hellopeter. Got an email response offering to contact me on another overseas number which would be at my expense. Bottom line. The debit order is still not changed.