3rd Party Claim Gripe

Can somebody please advise? I was involved in a car accident with a Company Car that is insured with Old Mutual Insure on the 15th March 2019. OMI asked for 2 quotations and the cheaper one was R39 000+ and Old Mutual told me they had discussed the quoation with the Repairer and agreed that my car would be fixed for R29 100+. I refused to sign for that as the Repairer denied ever agreeing to the R 29 100+. Now these guys are telling me that they had discussed the quotation with the Repairer and agreed to the R29 100+ so that is what they are prepared to pay aws they say, upon payment, I should go buy the parts myself and take them to the Repairer who will then continue with the repairs. Is that how 3rd party claims should go, is Old Mutual Insure supposed to send me shopping for parts, if so, at whose expense? I live 155km from Queenstown and Old Mutual Insure is sending me shopping for parts as a 3rd Party claimant and nothing is said about the expense involved when I go shopping for parts in Queenstown. I really don't think this is how things should work and am being bul**** by a big corporate.

Here's an extract from the email they sent me, "OMI does not make provision or pay for the part price markup as you can source the parts yourself and then the repairer can continue with the repairs."