Dissapointed client.

I have been a client since Feb 2018, and have a cellphone and LTE wireless contract. Now I would like to upgrade to 4mbps uncapped home and did apply instore, and they told me theres some error. My account is also fully paid up. Tonight at 11pm I recieve the following sms. "Dear Customer to enable us to process with your service installation a deposit of R700 is required to be paid withing in 7 days on BAN number ********** 39 to make an eft payment please use the following ref.......... Now my problem is Since when must I pay a deposit when thats not even mentioned in your adverti*****ts?? I app**** for a 24month contract, no deposit or upfront payment is required. Please explain. And if this is the case I will cancel it. I cant thumb suck R700 out of no where when there was no deposit advertised in your ad in the first place.