Shit happens, cut them a break.... but it's up to you... Me, personally, I'd spend the 5 minutes it would take to give them a call back. Because I know they are going to a quality job and not hack my car up.. Rather then be all butt hurt over a missed phone call.......

They're a pretty busy shop with a bit of a waiting list for big jobs... Not like they're just putting you off because of some personal vendetta.