Bike shop says can't repair bottom bracket

[Bendbiker]

I have a steel bike. It has developed a grinding sound in the bottom bracket. I took it to our local shop and they replaced the bottom bracket but the fix didn't work. They say I need a new bike. I'm baffled. If this were the case - I needs a new bike - it would mean a problem with the frame. There aren't any cracks in the bottom bracket shell. What else could make this happen?

[DaveM]

Maybe the threads in the bottom bracket shell of the frame are stripped out.
I've seen people JB Weld or otherwise glue BBs into frames where the threads are severely damaged to get a little more life out of the bike. It's not great, but might hold up for a little while. Probably no shop will want to do this for you though.