After using a T-mobile SIM card for a month in the US, my primary SIM card through telcel in Mexico doesn't work. I have a new card, updated software, and gone thru the steps with apple. Is it possible that carriers like T-mobile lock the phones?

After using a T-mobile SIM card for a month in the US, my primary SIM card through telcel in Mexico doesn't work. I have a new Telcel card, updated software, and gone thru the steps with Apple. Is it possible that carriers like T-mobile lock the phones? Could there be a hardware problem all of a sudden to do with the phone not recognizing a SiM card? TelCel said Apple needs to unlock it, but it was unlocked already, and i spoke to Apple card, too. What could i do now?