The frustration with GTL is completely valid and extremely common. They operate as the exclusive carrier at thousands of facilities, which means no competition and no incentive to keep rates reasonable. Families end up paying whatever GTL charges because there is no alternative on that end of the call.
The first thing worth fixing regardless of whether you use InmateAid is to stop accepting collect calls. Collect is the most expensive rate GTL offers, and every call you accept that way is money handed over unnecessarily. You need a prepaid account set up with GTL directly so calls come out of a funded account rather than being billed as collect.
From there, InmateAid's approach is different from simply putting money on a GTL account. The rate GTL charges depends on the number being called. In-state numbers are billed at a higher rate than out-of-state numbers at many facilities. InmateAid's system analyzes the rates GTL charges for your specific number and location and determines whether a different forwarding number can get your friend to you at a lower published rate. If it can, you get assigned that number and the savings kick in on every call. If InmateAid cannot save you money in your specific situation, they refund the transaction. That guarantee is what makes it worth trying.
To get an honest estimate of what the savings would look like for your specific facility and location before committing, email aid@inmateaid.com with the details. They will tell you straight whether it makes sense for your situation.