Europcar tyre ****?

Rented a car in Durban In Oct 2017, noticed a nail in tyre on return, noted on the return sheet. About a month later received sms to call them and was told they had to replace whole tyre at cost of +/-R4000. I objected, saying a patch costs R120 and they said they don't patch tyres, it's not safe. After disputing this, they agreed not to charge me, to investigate and get back to me. No word from them until 26/3/2018 and now I get sms threating further action if I don't settle debt. I took 3rd party insurance so it won't cost me anything to pay for the trye but this sounds like a ****. They never sent me a copy of the replacement tyre invoice as I requested and there is nothing wrong with patching a tyre if the damage is not in the wall or edge of the tyre.