Comment by mynegation

Cannot access spreadsheets now, but limiting free trials to one bank account would be the first thing that I would do. The second is to offer annual plan with a discount. The industry practice is to price annual as 10*monthly price (aka "2 months free"), and play with these numbers. That does introduce another parameter to the model though: the separate conversion rates to annual and monthly (or - how these 6% would be split).