Can I contribute more to GEPF?

I am an employee in a state hospital. I am a member of the Government Employees Pension Fund (GEPF) and of a retirement annuity (RA) fund. Can I increase my contribution to the GEPF? If so, by how much? Will the additional contribution be tax-deductible? If so, do I have to claim for it separately, as I do for my RA contributions? If I cannot increase my GEPF contribution, by what amount can I increase my RA contribution to benefit from the changes to the tax-deductibility of retirement fund contributions introduced on March 1? Dr RR Chetty