I was trolling a bit. You made the comment that it took 30% of the battery while sleeping. The device is not sleeping at all. The display happens to be off, but there is plenty going on in the background. You may have some control over some of these services, depending on your device and what software is installed.
If you just want a phone then buy a "feature phone". It's operational and power model is mainly driven by the cellular network it is communicating with. Any add-on features, like web browsing, are tacked onto the side and are often very limited in their functionality as a result.
If you want a pocket computer that includes a cellular modem that happens to use the same network as a cellular phone, buy a smart phone. These devices are like laptops. They sleep as much as they can, but wake often because of the background work that has to be done to provide the services that are expected on such a device. The cellular modem inside is working much the same as the phone you used to have, though it works a lot harder because of many active data connections held open by services running on the device.
It sounds like you bought the wrong type of device. It helps to understand the trade offs when making such a decision.
