Using Unlocked Iphone 14 pro with prepaid t mobile esim- going to India soon so what international roaming plan i need to activate

I was in India in Sept and Oct 2022 with an iPhone 14 Pro. The T Mobile Unlimited cellular data worked nicely almost everywhere. Including Delhi and many other Indian airports, New Delhi, UP, Madhya Pradesh, Chhattisgarh, Odisha and West Bengal. Worked in rural, small towns and cities as I travelled 1000s of km across India.

It was slower than data plan in the USA, but I was able to get text/SMS messages, WhatsApp, Email, etc.

Occasionally, I had to switch off the iPhone and reboot it up to help it to re-login to the best signal cell tower.

No surprise shock bill charges by T Mobile after the trip. Yes, I have received the bill that covers the travel period in India, after returning back to the USA.

I have the Magenta Unlimited plan. I do not work for T Mobile, nor does anyone in my family or friends.

These were my phone options → Settings : Cellular → then Cellular Data : On (Green); Cellular Data Options : Roaming On; Personal Hotspot : Off. T-Mobile Turn On This Line : On (Green); Scrolled down and confirmed that all the desired Data-driven Apps were On (green).