Some key rules I've found are to avoid the challenges you're describing are to evaluate quality (use the software + check their docs + talk to customers) and portability (actually make sure the exports work the way you need them to) before considering using or recommending any new piece of saas

Working on a search/review/ratings engine (https://tooltip.com), that currently operates as a consulting service, because I've found that parsing through all the muck is a waste of human time and anxiety (also, ppl often end up on the WRONG solution because they didn't have enough time or the right resources to search)

Edit: More immediate practical strategies are to use a spreadsheet that aggregates up from the dept level to the company level to keep track of all users/accounts, or buy a piece of SAAS to manage dedicated procurement / billing (there are a few alternatives out there on this front nowadays)