Grandfathered Simple Choice

I realise this is an old thread but im going to ask anyways. We are on a grandfathered plan as well for this. My husbands been on for 7 years and i have been on it for about 3. We were under the understanding that all data through this plan was shared and that it would be a cheaper route for us too go. We recently looked at our billing statements because we were wanting to get onto our own plan. By the looks of our bill i can see(not the main account holder) for 4 lines the bill comes too just over 200 and thats fine. All phones are paid off. we noticed that the 2 on there were much cheaper and the main account holder has unlimited with the bill being about 30 dollars a month for each but my husbands bil says its 80 a month with fees and mines 60 or so with fees. so we alone are paying for our 2 lines on this plan 130- 140 of the bill. when i look at our individual accounts with the no access it says we should be paying around 90-100 for ours which would make sense because of the bill total. isnt it shared data on the plan and why are we having to pay extra for our data when the main account holder does not? We are told that its because of our add ons but when i look at our add ons we dont have any extras that would amount to this total cost. now we are trying to figure out why our bills are quite abit higher then everyone elses. i looked and there is only an option to either pay the amount for the plan fees and then pay for 30 dollars for data and have no data? how is that when the others are paying a set fee with such a low amount? no one will give me answers to this question. its like were paying the entire bill basically ourselves. How on earth is everyone else getting such low rates and we seem to be bleeding money on this plan?