Can a collection agency report the same collection account under 2 different account numbers on your credit report?

Yes actually they sell the account to differant collectors and will continue to blemish your rating until it is paid in full/ settlement or you request the item to be removed for lack of authenticity

Answer

Sorry, a single account cannot be sold to multiple collectors at the same time. Sometimes a collector will update an account making it seem that the account is active,and the reporting data is in error, such as transposed numbers, or even the number of someone else's account. Regardless the reason, it should be brought to the attention of the credit bureau(s) and if found invalid,should be expunged.