Overcharged then refund not done per policy

Purchased 2 bottles off shelf medication, was overcharged (Marked R66.40 on shelf rung up as R71.50). Spoke to manager who said refund would be performed. Person doing refund then did refund of R10.20 while sitting underneath the very large \double the difference\" policy sign. When queried on why policy wasn't being app**** the response was \"you heard the manager say refund the difference\" and was unwilling to engage further. This is completely unacceptable. At this point I left the store - and wont be going back. When your staff wilfully engage in disobeying your policy to the customers detriment (and appear to be doing so consistently) then it is not an organisation I wish to do business with. "