I think you need to clear this up with the agency. Ask them how they got the WES reference number. Sorry man, but something seems fishy here. if it were upto me, I would never trust an outside agency to do a simple job such as this.
Right, so how did they get the WES number? If you have already paid your agency an equivalent of 322 CAD, you really don't need to pay or do anything else apart ensuring that the docs your university sends has your reference number on top of the envelope.
The fact you must understand here is, no one can give you a WES number without paying for it upfront.