All questions are in bold for ease of use.
The major carriers in the United States participate in NSA surveillance (except for T-Mobile apparently, because it’s based outside of the US. Except they bought Sprint, which participates.) and that, along with other major privacy issues, means that the market for private carriers is incredibly slim. When I found out that some carriers, such as Mint Mobile, piggyback off of Verizon, I wondered: What’s stopping a carrier from simply E2EE everything from Verizon, and then using Verizon to transfer the data? Obviously, the encrypted data could still be collected and sold, but it wouldn’t matter if the encryption was setup properly, right? I’m looking to better understand how this works, and, if a solution exists, potentially be the first to make it happen. The reason I’m not suggesting creating a carrier without piggybacking is due to the sheer cost and lack of support it would have, which would lead to poor adoption. Also, if carriers simply don’t support E2EE, couldn’t carrier locked phones install the software (since most install software anyways) required to make E2EE work?
Do you mean E2EE for voice calls and SMS? Otherwise why not use a trusted or personal VPN to solve this problem? I wouldn’t bother with trying to secure voice calls provided by a carrier as the recipient would also need those counter measures in which case why not use ab E2EE voice app like signal.