Who I have the same questioned this topic

I am abroad, I bought the phone in America. After 3 years, I did a factory reset and my phone could not activate without a US SIM card. I found such a sim card, an old verizon that had not worked for a long time, inserted it into the phone and activated it. Now my phone is verizon locked and won't work with other sims. What should I do? I can't get a working Verizon sim, my phone is locked.