Simple Procedure Scotland

[Ally2000]

I received a notice of claim issued by Nolans on behalf of Cabot for £2207.46. I contacted them to settle before the last response date but they replied that the amount was now £2610.31. When i queried this they said they had made a mistake and it was £2502.31. They said the extra was court judicial expense. I replied that I would settle the £2207.46 and they have replied that i must settle the £2502.31 which they now say includes expenses or I will be taken to court. Are they allowed to add expenses if I'm willing to settle before the last response date?