Issues with selling shares

I have been trying to sell Massmart shares since last week but the platform keeps showing "You have insufficient funds to purchase this equity at the moment. Please deposit funds into your account. Alternatively, if you do not have funds right now to make this purchase, set up a Recurring Investment and choose when it is convenient for your investment to take place via debit order" YET I AM TRYING TO SELL AND NOT BUY! Why in the world will I need money to sell an instrument? I have been investing with this company since 2014, and honestly their service was exceptional until now. Never had I in the past logged a ticket and not got a response with 12 - 48 hours!

I am so dissatisfied as I since logged my ticket (871266) last week Thursday. I have lost 3% of my potential profit so far and this is bad service:(