Hi jackiebee,
The Medtronic pumps are the very same size. It's only the reservoir that's a different size. They both fit into the same pump. You choose which size reservoir you require, based on your insulin requirements.
I use a Medtronic Paradigm 754 'Veo' and have found the customer service to be second to none.
Ordering fresh supplies is simple and straightforward, by either telephone or via email to their store.
I've recently had cause to telephone customer service and speak with someone that took a great deal of time to explain things AND make sure that everything was working as it should before he 'gave up on me', with no qualms about how long the call was taking. (I needed to move from one room to another to fetch supplies that I had, and that's not an easy thing for me to do due to mobility problems.)
It's been a few years now, but I needed to telephone Medtronic 'out of hours' due to a problem I was experiencing with my pump. No problem as they forwarded me a replacement pump within 2 days, and return packaging to return the pump that I was experiencing a 'problem' with so that they could investigate.