Unwilling to assist effectively

My car was booked in with them on the 15 January, I only found out after a week that the car is with them and not the intended autobody shop, however I was happy for them to do the work, little did I know that, that will be the beginning of my headache, at first they told me it will take 2-3 working days for the parts to arrive once the got the authorisation from the insurance, on day 4 after the initial SLA when I called, I was told there was one part that was incorrectly ordered but it should be arriving the following day which was Friday the 29th, later that day I got an email saying that it takes 6-8 working days for the parts to arrive, I then sent an email to confirm when does the 6-8 working days start, to this day I have not received feedback. I have been calling them every second day with no joy, the last call I made to them I was told that the parts that arrived that day was missing one part which might only be available on the 22nd Feb, which i find ridiculous because there is no way that Hyundai doesnt have parts available.