To given extent it can, but it requires you signup for a free account with a SIP service provider and be placing your trust in that party, or go the extra miles and setup your own private branch exchange on your server.
After having gone through this process a dozen times now, I've learnt to appreciate that I now only have to worry about my colo provider.
>impossible to secure your calls on a phone
You can secure them to a certain extent.
The content of your conversations with something like Signal, Jitsi or any other VoIP client with SRTP and ZRTP supported would remain confidential, but the who was called, timestamp of call, duration, location call was placed, towers your call data passed through will remain known to your carrier.
>feel like I'm constantly being tracked
Sorry to hear tyou're experiencing that.
Can I ask, where did this come from?
...You mentioned being anonymous and wanting privacy.
If you want these plus security, carrying a phone reduces the chances of both the first two dramatically.
Doesn't mean go full on stallman.
You know you're threat model better than anyone else here, so just set some time aside to understand what it is you want.
Good entry point for getting to grips with this is reading https://grugq.github.io/
Past case files, slip ups of others documented regularly https://cryptome.org
, and for take down coverage in the markets http://deepdot35wvmeyd5.onion