Non Delivery and bad service

My husban Xavier took our ecu for our vw sharan in for testing and they said the box needed replacement which we glady accepted and paid for the replacement which took a whole lot of time prior to the lockdown, after having received the replacement which didn't work at all, was advised to tow the car in, he gladly did, which cost money, after 6 weeks of them having the car, it still had the same issues which they charged us for and we paid, then took the car to several auto technicians whom all confirmed it wasnt an ecu issue as the old computer box was still in perfect condition and works well with the car. Went back to them with my findings, they replaced several boxes to no avail and now demanded my money back. To my greatest shock, they only recunded 50%of money back which was r2000 out of R4000 hiding behind terms and conditions and for heavens sake, which company or person charges you for non delivery? The thought of Ronnie's audacity to say they're not liable after several supplies which did not meet my requirements as a client to go fix my car before complaining and hung up. I even drove the same car with the old ecu box to their offices just to prove my case to them fell on deaf ears.