Beta Baths won't refund my money!!

Stephen Lambrick and his team refurbish a bathtub for me last month. He asked me when he arrived for the job to pay him the same day. I was working until late that night but I kept getting text messages from him about when I would pay and if he could expect payment by the end of the day. I found this excessive but when I got home shortly before midnight, I went straight to the computer to retrieve his invoice. He had billed me R1800 instead of the R1600 we agreed on. I texted him about it. He replied immediately and apologized. He said R1600 was fine.<br> The first attempt to pay through online banking ended up with an error message. Thinking that the payment did not go through, I processed it again. It was only the next weekday (Monday) that I saw that the payment had gone through twice. Since then, I have called Stephen Lambrick (no answer), texted him (only responded twice...second time promised to refund my money) and emailed him (no answer). He was in such a rush and he pressured me to get paid but now that I have paid him twice in error, he doesn't seem to care about returning the money. Beta Bath's professionalism and integrity are at stake. Please refund my money!