When I am telling other people about Ting, they are concerned with overages. I think this is a valid concern and it could be answered by offering a way to pay a flat fee to get unlimited use of the item in question.
Minutes (Current tier maximum: $35 for up to 2100 minutes): $40 a month for unlimited minutes.
Text (Current tier maximum: $11 for up to 4800 texts): $15 a month for unlimited texts.
Data (Current tier maximum: $20 for up to 2GB): $25 a month for unlimited data.
Monthly Maximum: $80/month
This allows heavy users the ability to have peace of mind with unlimited features (for a fee comparable to other carriers), while allowing normal users the flexibility to focus on certain areas they might use heavily. I think this will not only attract more users, but increase revenue from current users by allowing them to buy in to unlimited tiers of their choosing.