Yup...I bought 2 phones but both have issues...As u said buttons were not working correctly after few months...Even after sw updates by OTA and jio company it got issues in few days...
Now both r not in use...Wanted to sell but demanded for rs 200/-...
My experience is worst with jio phone,main problem was with its buttons, hanging problem,bought 2 times for father ,one for mother ,all have same problem, so finally I bought nokia 4g phone
If it's keypad mobile then only one model available now in all the jio Store the one I bought .. if it's smartphone then different variations available based on availability on appropriate Jio Store or Local mobile store