Internet access

Hi Folks, if anybody has any answers to my questions I would appreciate it if you would pose it in language that an older, none techy, can understand!
I bought my i530 on the understanding that I would be able to connect to the internet using the phone as a modem. I had in fact been doing just that with the Sprint service I had before. I live on my sailboat and for the past year I have been on the dock with a land line so had no need to set up the Nextel internet service.Heading North out of the hurricane belt soon so decided to get my cell phone hooked up to the laptop. Managed to download the USB stuff and get the phone to dial but it immediately came up with "number not in service" message. Not true because I had been on line with my stoneage dial up ISP just moments before. I called Nextel only to be informed that I had to pay a $40 a month fee for this service. 4 x what I pay my ISP. Can't afford it. Anyway why do Nextel have the legal right to block what I recieve on my phone useing time that I have paid for??? it's a local call and it should not be of any concern to them wether I dial a porn chat line or a computer.
Any solution including a different cell phon service welcome. Now I need a drink!!