I've heard they're pretty backlogged, but if you are going to contact them I'd recommend you contact them through the online webform rather than calling.
In webform can attach the receipt again and also (if you have one) attach a screenshot of when you initially submitted the receipt on October 21st... proves that you've paid almost a month ago and are still waiting for the request.
If you call, I've heard most people are on hold for hours before they get to talk to anyone, and that often the call centre agents are misinformed and/or speak outright lies. Overall with calling, it doesn't sound like the agents are very helpful.