two routers from same model but one support same network operator other don't

[y2ktoys]

there are two routers from same model.as it's seller say both will support every telecommunication operator in my country.so i bought one for me.one of sim from telecom. operator work fine with my router.it show signal streath and other data on router home screen.then my relative bought a router from same model,but unfortunately it did not support same operator as i mention above.no service on router home screen..we tried 3 sim from same operator ,but same result.no service.

then we insert another sim from different operator.it works fine..

how can same model of router response differently for one operator?

sim slot is not damaged .what will be the reason for this?

[Geek-9pm]

After reading your post I wish to bring your attention to three areas of importance.

First problem. Routers have a wide range of settings that remain even after the powers turned off. This is by design, they are supposed to work that way. Changes in the settings will change the performance of the routers even to the point where a router might not even be recognized by other equipment.

Second problem. The router firmware in some cases can be altered without there being any visible evidence that it is been changed. This is a common practice among many amateurs as well as professionals.

Third problem. All routers must have some type of unique identification built into the router. This is a requirement. This feature is often called the MAC  address. Every router must have some MAC address that is only used by that router. In some cases two pieces of equipment might use the same MAC address, but this is considered to be an exception.

My local Internet provider here in this country will not let me change to another router of the same model number. I have a spare router, but I'm not able to use it because the service provider looks for the unique MAC address of my router. If I need to substitute another router for any reason, even a router with the same make and model number, I must contact them and explain them what I am doing so that they can set their equipment to recognize a different MAC address.

To make this story short, you must contact your service provider and ask them for help. They may charge you a fee for the service.

This is the best I can do for you.