What to do with my locked iPhone 5s, how to activate?

Hello,

So my uncle went home here in the Philippines from Austria and left me his iPhone 5S that is unfortunately locked with T-Mobile. I gave him back his sim card. He want back to Austria and after that I did a factory reset to erase all the data and now I can't activate the phone after updating and resetting it. 😟

What can I do? I don't have the original sim card to open it and at least use it as an iPod. Is there a way to activate or unlock it please help me.

If not fixed, it's just going to be dumped here forever! What a waste just when I needed a new phone.

Help?