So you're shocked, shocked, that a company might market their product using specs that weren't based on real-world use?!
Honestly, if all you did was review manufacturer specs before buying an entirely new type of phone (or any product), I'm not surprised that you're surprised.
There are a ton of discussions, in pretty much every smartphone forum, about battery life issues, and it's never talk about how the phones meet or exceed manufacturer specifications.
All this information was out there before you made your purchase, unfortunately you didn't avail yourself of it. A lesson learned for your next shopping activity. I don't even purchase "dumb phones" for my kids before reviewing forum discussions and any available tech site reviews for issues related to call quality, signal capture, battery life, reliability, etc. There is a ton of info out there if you go looking for it.
Manuf. specs are all a numbers game...manufacturers in pretty much any industry work the the numbers, ensuring they are legally accurate while attempting to make their products' numbers impressive and superior to their competitors. if more consumers were better shoppers and didn't rely so much on what the manuf. told them they would be better off.
If you're within your 30 days you many want to return your phone and stay w/a feature phone, where you can get great standby/use times (my kids ENV2 phones can go for days w/regular use w/out needing a charge).
If you're outside your 30 days there is a lot of info on how to prolong battery life...spending your time on that information, rather than wondering about manuf. specs, will be a much better use of your time. Good luck...