Where I live, the friendly guy next door (quite literally) does all the modern BMW. His wife accepts to order for me the parts to keep my 30 years old machine running. Often she does not get what she ask for. But she keeps asking for them and one day, after month of waiting (yes months !) the part finally hit her counter...
Bear in mind that some parts are seldom bought so not in stock anywhere and have to come from either a big warehouse in Germany or a contractor factory.... This takes time.
Phone them and inquire about the status of the back ordered parts. And, depending upon the answer, ask for refund.
The whole commerce is based upon trust. I trust my friendly part dealer. I know she is trying hard to get me what I need/want. So if she doesn't had what I asked for, I know she will get it one day or call me to say : "nobody has them anymore. What should I do ? Could we find an alternative ?" ....
Talk to them.