ATPs / SMSs may work for hospitals and clinics, not only DMEs. They can also hold OT or PT credentials with an ATP on top.
You may see an SMS after someone's name (seating and mobility specialists, an added credential for some ATPs). PTs and OTs without RESNA certifications may play a key role or be rubber stamps. A clinician must sign off on orders for reimbursement to avoid "conflicts of interest" (eye roll).
It's important to look critically at the recommended chair brand/model and configuration before it's submitted to your plan, particularly if that person works at a DME vendor, because recommendations can be skewed by compensation/incentive considerations, even by the month or quarter. Also, accessories that PALS find important can be overlooked or accidentally omitted, and harder to get later. You can find a lot of information on line, including here, about pros and cons of chairs and features.
You have the right to work with any DME firm in-network with your plan (of course, if you pay cash, you can work with any DME at all), even if your clinic does not normally work with that provider. Clinic/DME relationships are not always based on merit.
It is not unusual to switch DMEs before an order is submitted, if you aren't a fit or question their recommendation. We did (going from a Quantum to a Permobil).
Switching DMEs after taking delivery is much more problematic because they make their money off the new chair order, not add-ons (unless major), maintenance, or battery replacements. And with short-staffing and dwindling reimbursement, few vendors can afford to spend significant time in low-margin activities.
