Should eleven-years-old use mobile phone?

Mobile phones are essential for our daily life. . If you look around, everybody uses them and teenagers want to have one, even the youngest, the eleven-years-old and usually their parents buy it for  them. However, using them have some advantages and disadvantages.
The main advantage is that you can call or text them to know where they are and what they are doing and you can inform them of your own plans. Besides they can use their mobile phone to get  information for school works.
On the other hand, there are disadvantages. A lot of teenagers have their mobile in their bedroom during the night and they can be amused for hours. As a result, they sleep less than they need . Besides  there may be problems, such as   cyberbullings  , which are very serious.
In conclusion, I think the best way is that parents make them obey some basic rules for using their cellphones  and limit them for  using their cellphones and check their devices  regularly.