Bonitas asks for one thing then changes their minds like we have time to run around

I sent in my option change form to Bonitas, the option change form clearly asks that if you earn a goverment pension sassa then they will need a copy of a withdrawal slip from a sassa paypoint confirming your montly pension, I have forwaded them my sassa withdawal slip and now they send me a mail saying that" Kindly be advised that your option change has not been processed as you need to include proof of income including your 3 month detailed bank statement. Kindly forward all the relevant documents in order for option change to be done., I dont have a bank statement because I am a pensioner, and why ask for the withdrawal slip if you then want to ask for bank statments, why ask for one thing and then when we give it you ask for something else