Sure thing! Behind every "unlimited" plan out there, there is a per minute rate that small carriers like us have to pay in order to get access to the regular phone network and connect to any phone number in the world. On top of that, there's a monthly cost per phone number, per E911 address registration, per voice channel, etc. Then, you have the ever popular "taxes and fees", which can vary based on the user's location and can become complex very quickly. Not to mention FCC registration fees and taxes. Then there's the cost of the server infrastructure to register the phones and keep them online. And finally - STIR/SHAKEN implementation has a cost of registration and verification as well.