Yes, you are not required to hold your certification with any provider for any period of time. You can even change between a stage 1 and stage 2 assessment if you wish. You can change it at any time of the process or time of year.
The only advice we would give is to not request a transfer if you already have an assessment planned with the current provider within the next 30 days as this could potentially incur costs from the current provider. In these circumstances we would advise you to wait until just after your next assessment.