POOL TEAM Charges for sand change even if not done

Pool Team Randridge mall advised me to do a sand change, as the previous one had been more than a year ago. I booked a sand change, for which I had to pay R1190 in advance. The team arrived the next week, but were unable to open the filter (*****s wouldn't come out). Since they didn't have the rights size *****driver with them, I assisted with what I could find, along with some WD40. Nonetheless, they were unable to open the filter and left after approx 20 minutes.

The next day, I promptly received a quoite on a brand new filter system (only R5990) which I declined. Naturally, I requested a refund for the sand change. First via e-mail (ignored) and then in person. They refused to credit me immediately via my credit card (which was how I had paid) and made me fill in a form which would be sent to "Head Office". I did however receive a little printed note saying I would be refunded R1190. A week later, the manager phoned me to tell me they were subracting the "callout fee". I told her I would not accept that, since I has paid a once-off fee for a sand-change and nowhere was it broken down into callout/sand change, etc. As I had not received a sand change, I expected a full refund. Many calls to the shop later, no feedback was received, and now I see they actually refunded only R710, and they had therefore actually deducted a callout fee, against my wishes and contrary to the refund slip they had given me. I think I might start a company promising sand changes, not fulfilling the sand change, and then charging R500 for not doing anything. Seems like easy money. To be clever, I'd then sell them a new filter!