My first thoughts are what evidence have they provided to you that it is the pump? What fault codes have they provided to you? Pop them up here if you can get them along with your VIN and we can check the faults first.
Second, If it is the ABS module itself, they are often programmed to specific vehicles and engines, especially of your vehicle has ESP. So what you have been told about having the correct part number is accurate. I must say, I'm not getting good vibes from what you're telling me about the garage you are using.....
Lastly, we can help with official part numbers, but this is a chargeable service we have to pay for, so requires a membership upgrade for us to respond to these requests (please see details below), so if you are sure it is the ABS module and can't check the label to obtain the part number yourself, you may want to consider this as an option:
We can help if you need an original genuine part number, part diagram or vehicle factory build sheet and can't already find the info you need on the Forum. For this service, we do ask for a membership upgrade for official parts data as we are in turn charged for this. It will cover you for future part number requests for up to 3 years, so excellent value.
If interested, links are below, then provide your vehicle's VIN in full, which will be masked automatically when you submit your post.