Whats his monthly cost now ?
Sounds like he's on an old fixed/capped MB usage package. Only used for those that think they can save some money each month because they don't use the Internet much. Unfortunately your elderly uncle has found out what most mobile phone users find. The devil is in the detail and the company makes its money from the unwary, who use the product more than they anticipate.
Linda, I don't know the cheapest package. or best package but I'm on AOL and for instance their cheapest uncapped connection rate is :-£14,99 with no limits.
Check it out.
As you say no doubt Codders will give you better advice but its a start.