Mark may respond better once legal proceedings are underway. I aim to get my refund willingly, or otherwise. I have not witnessed such a shabby affair as this in my life. If Mark doesn't want to be an honest businessman and make good my refund, as his word stated, then there are repercussions. This whole issue has been documented and has been passed on to the relevant authorities.
I was taught about honesty from a very young age. I was also taught about what happens otherwise.