I think you'll find it hard to get them to pay much more for your service, especially if they've been paying customers for less than a year. I'd advise seeing

I think you'll find it hard to get them to pay much more for your service, especially if they've been paying customers for less than a year. I'd advise seeing it as a learning opportunity, how much of a loss do you make on these users? Are there any ways you can cut costs to compensate? Other wise, try raising the price for new customers to a point that if the old customers were paying that you'd make a profit. I bet you won't see a drop in revenue