Can my company take my commission without compensating me?

Hi all,
I have recently moved position from a sales position to an administrative position. I was earning approx 2k commission per annum (not much but every little helps) which I am not earning now as I do not see any customers.
My pay review for changing to this position was put on the long finger by the employer and the loss in commission was not factored in. I have tried speaking about this but have been ignored.
I want to stay in the position I am in but not at a financial cost to me. If they refuse to compensate me for loss of commission am I entitled to go back to sales and retain my commission? There has never been a discussion about this and that is what irks me most.

plenty of sales jobs out there, but as its a bonus based position why would you expect to earn the same amount when moving to a easier type job role

not trying to wind you up but sales and admin are different types of work

Without knowing the full circumstances, I guess a lot would depend on whose decision it was to have you change positions in the first place or the circumstances under which the move occurred. Presumably there would be a big difference in the strength of your argument had you chosen the administrative position or whether it was imposed on you by your employers.

The admin job is a lot more high pressure than the sales as it is not an intensive sales position. the position arose and we were all asked if any of us would consider it. i said I would. My review was due anyway and I was planning on negotiating a pay increase for the admin job due to the extra work and loss of commission. However my new contract was just sent to me with no discussion and a minimal increase. So i am actually earning less and working more.
My main inquiry is if I choose to go back to my previous position which is still open and in the same office etc are they able to take the commission from me. The commisssion was negotiated at the start of my time with them (2 years ago) and I have not signed/agreed to anything in relation to the new position.

Problem is , you should have finished money negotiations before stating new role.

Employer may say they have filled your old position, and you are now complaining because of new workload.

Not much anyone can say, you need to approach manager and raise your points , and see what he comes back with.