One idea might be to focus on trying to convert monthly subscribers to yearly. You could offer a subset of monthly subscribers a one-time upgrade to a yearly s

One idea might be to focus on trying to convert monthly subscribers to yearly. You could offer a subset of monthly subscribers a one-time upgrade to a yearly subscription at a prorated discount. So people one month into their subscription could get the remaining 11 months for the annual cost minus the 1 month fee they already paid.