I need 13, not 12, pre-packed medications per annum

My Chronic medication is prepackaged for 28 days and cannot be split. My repeat is never available on the 28 day basis. Despite getting these repeats for about 10 years on time, for the last 6 months or so the Discovery Health system is pushing this out to 31 days. It is positively frustrating talking to call centre staff and Ishmael in Pharmacy as they do not seem to have the intelligence to work out that 365 divided by 28 means I need 13 per annum, not 12.