If I paid the full cost why is my iPhone locked?

So, cellphones. I bought my first cell phone in 10+ years 8 months ago. I'm still learning how it all works. When I bought it I didn't get a discount (I paid the full cost of the phone, like $600 plus set up fees and everything) but it seems it's "locked" to Verizon anyway. (I thought if you paid the full cost it would be unlocked… And now I feel like an idiot)

If I want to:

1.sell my phone
2.switch providers

how can I do it? Also, I make only 5 phone calls a month on my iPhone. But I use the data plan HEVILY.So, I need unlimited data and not much call time. Maybe there's a better plan than the expensive one that I have now.

Any providers good for that? Paying $80 a month to Version is getting old.
But maybe it's what I'm trapped with.

Yup you misinterpreted somehow. You have 3 options when buying an iPhone

1. The $199/299/399 2 year contract option
2. The $599/699/799 no contract option
3. The $649/749/849 unlocked option

You could sell the phone, but of course the person you are selling it to would have to know that it is locked to Verizon. Depending on which iPhone you could possibly switch to a GSM carrier.

You'd have to talk to Verizon about it though.