Wrong contract issued, failure to correct this

On renewal of contract in March my husband asked for EXACTLY the same contract as before. I use the phone and in April received a voice message that my air time is almost nil. That was the first time we became aware of the fact that we were issued a top up contract in error. Because my husband is very seldom at home, traveling extensively for work, I personally drove from Melkbosstrand to Tableview to sort this out. Needing my husband's permission to correct their mistake, the Bay Side staff, after some time was able to contact him via cel phone. The correction was then supposedly done. The correct contract was to take effect beginning May. This morning I got another voice mail that I'm low on airtime, i.e. we are still on top up. The call centre say they cannot help since they cannot reach my husband on his cel. I did explain that he's in a board meeting in Joburg. Call Centre says they cannot get info from Bay Side and sort out. The mistake was theirs in the first place and a month after personally calling on them it still had not been done. They **** to me! What must I do to get them to sort this out????