on-call payment rates for uk basic grades

I am interested to know how other trusts pay uk basic grades for participation in on-call duties.

The CSP changed its guidance to recommend that the competency level for a basic grade working independently equated to point 4 on the band 5 scale. pre AfC this had been paid at senior 2 rate.

Since other on-call terms have not been argeed this has not been implemented. Any overtime i work appears on my pay slip as a rate which is even less than the rate which would be equate to my current annual salary. Since i do a substantial amount of overtime i feel i am being underpaid by as much as £2.50 an hour! The payroll department have told us that the current rates are pre AfC rates ,so should it not be at the higher sen 2 rate? Our payslips are pretty much designed so that you don't understand them anyhow. Anyone else found themselves in this situation? how have other trusts interpreted the changes? any advice would be good before we take it forward to the rep!
cheers in advance
Laura