Problem when topping up data plan

I have an iPad 3 with a 3G plan from network provider 3. The problem is that every time my data runs out and I top up, I have to reset network settings to get online. This, of course, means I lose all my saved wifi passwords ... a royal pain in the backside. Is there a quick solution to this within my current set up, or will I need to arrange a new form of data contract?

Are you topping up before the plan runs out? Letting the old plan expire before topping it up may possibly be the cause of the problem.