I would tell my friend about the disadvantages of using a mobile phone all the time.
I would also ask him/her to always be in touch with your friends and never lose this relation.

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I would first convince my friend so that he/she will use the phone less and only when it is in use. I would even ask his parents or guardians to take this phone away and give him when only he completes his studies. I would make my friend to come down to one point so that he will use the phone in less and limited way. I will even ask my friend even to stop using the phone and teach him the consequences when we use the phones.    
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