The Nokia 206 is a basic phone stuck somewhere between the Nokia Asha 310 which has a 2MP camera and the Nokia 105 which has no camera at all. This phone has a 1.3MP camera and and is dual sim but only 2G capable. The music play time is good at 41 hours however it is not going to work well for a very young person such as a teenager as the keys on the phone are wide apart and tends to gather dust and grime. The user guide for this phone has been listed below.
Note that because it only has 2G it might not work in all countries. It does come with GPRS (Up to 85.6 kbps) as well as EDGE (Up to 236.8 kbps). The screen is a TFT with 65K colors and large enough for use by older people as it is 2.4 inches (~31.1% screen-to-body ratio). As stated above there are other options as the limited memory of 4MB does provide its own issues.
Very basic phone and if you still want looks and style with a phone a bit better then there are other options as well such as the Nokia 301 as an example. You can browse this website for more options from Nokia and Motorola outside of the Nokia 206 as listed here.
See the user manual below for more information and assistance should you wish to have other details about the use of the phone.
Nokia 206 User Guide
You can download the user manual above of simple look at the links below for more assistance. These are much older phones and you might need to check if you can run WhatsApp on this phone. You can see that listed above as well.
Support for the WhatsApp older Java version is coming to an end in 2016 so consider installing it even if you dont use it as yet. Internet settings have been added above for more assistance. Search this website for more details.