Does a new wheel bearing have a mileage/time warranty? My "Y" Reg Subaru Impreza had a new left rear wheel bearing fitted at great cost last year. I've only done about 1000 miles since then.
Warranty or not there are consumer rights and fitness for purpose. A wheel bearing will have an expected life of thousands of miles - you one is therefore faulty and needs replacing by the garage that fitted it. It is you right. so do not be fobbed off by flannel from them.
It sounds more like it wasn't fitted correctly Chris. Wheel bearings go on for years - provided they are correctly lubricated and not too tight. My guess is that whoever fitted the bearing over-tightened it and it's now worn. If so, the only solution is a new bearing to replace the noisy (rumbly?) bearing which is ruined.
I would go back to whoever fitted the bearing and get a refund. Then find a competent mechanic to fit a new one.