This is another efficient and well tested formula. Whenever there is a need to raise fees or tariff rates, just offer a 3 month or 6 month rebate. This can be done right at the beginning or quarterly over a year.
The customers will feel grateful that they have a rebate, a subsidy mentality, and actually feel good. They will forget that for a few months of rebates they will eventually pay the new rate for the rest of their lives.