Dental & Vision

I am currently enrolled in a FEDVIP dental plan (mainly for the orthodontic coverage). My dependent has come to the end of this phase of treatment and we have used the maximum allowance under the current plan. I am thinking about switching coverage and understand that I would have a waiting period to use the orthodontics coverage under the new plan. I am being told through my orthodontist provider that since I have used my maximum allowance under one plan, that even if I switch plans and wait the waiting period, the insurance provider would not have to pay out since I used a maximum under a different plan. Is this true? Should I change plans?