I started to do my own work because of shops like the one you called. I think that whoever you talked to is upset that you didn't buy the strings from them but that is no excuse to bad mouth a reputable string maker like Hogwire.
Have you considered installing them yourself?
Is the Markhor able to fold the snow collar and create a lid like the Tahr and Argali?
Also, can you still run the guide lid if the bag is using the snow collar as a lid on any of the bags?