Braces question

I posted Afew months ago regarding my braces treatment. At my last checkup the dentist shorten the wire on my bottom teeth (I don't have braces on the top) so that it was only on the front 6teeth. I went back for another check up 2weeks ago to be told they can come off. I was meant to have them on for 18mths and I only got them in January. I haven't booked the removal yet as I haven't paid in full but I've actually noticed my first premolar has already moved back further. This tooth was like this 2weeks ago when the dentist said they can come off. I'm worried the dentist won't keep them on and put a new longer wire back o. and all this pain will have been for nothing a second time round. Not sure if I can go elsewhere as I have an epc plan that covered the majority of treatment. Has anyone had this happen??