"changing an electronic prescription"

I move practices after many years for convenience (nearer to home basically)

I've had an electronic prescription in place for some 3 years or more. The first time I went to get my prescription I've found they have changed it.

I take gaviscon to ease the symptom's of a hiatus hernia, I have to take them pretty much each time I eat so have found that the sachets are more convenient to carry than a large bottle. The new practice has changed it to a bottle without so much as a phone call. On calling them they have told me it is their policy to prescribe it in the bottle format and the medicine manager is not able to change this (although they had the authority to change it from sachet to bottle) I now have to book an appointment to speak to a doctor.

Is this allowed?

I appreciate that practices run different policies but are they allowed to change a prescription that's been in place for years without consultation?