Universal Credit appointment with Compliance Officer

I was wondering if any one could help.
I am a disabled lady receiving Universal Credit and after taking my fit note in to my local Jobcentre, I received a letter asking me to attend an appointment to speak with a Compliance Officer regarding changes that might affect my benefit.
My question is, has any one had to attend one of these before? 
I don't know what to expect as I've not had one before and the way they word their letters is really not very nice.
Thank you