Incorrect Upgrade

My Giga20 data contract expired and was running on a month to month basis. I received an unsolicited call from Cell C inviting me to upgrade the contract. I was told the conditions of the contract would remain the same and I would receive a free Huawei E5330 Router. However, what was delivered as a ZTE USB stick modem (and not the router as promised) and the contract was changed from a Giga20 TOPUP to a Giga20 POSTPAID. This is not what was agreed to when contacted by your call centre agent. I have made numerous calls to Cell C over the past few days, as well as sending numerous emails to have this corrected. To date, no one from Cell C has contacted me to arrange collection of the USB stick modem and change my contract back as I have requested.