Buy an unlocked Samsung used off of https://www.backmarket.com/en-us/l/smartphones/0744fd27-8605-465d-8691-3b6dffda5969#brand=1%20%20Samsung&sim_lock_state=Unlocked%20only

Edit: if you don't care about features you can buy a cheap $30 phone at regular stores like Walgreens, cvs, even gas stations sometimes.