这个不一定,要看你怎么用了
首先把cellphone简化成phone吧,这个用在口语上比较恰当...
如果是用手机和朋友聊天,是Chat with my friend on the phone
或者问,谁接电话了吗? Is she there? She's on the phone.这里也用on
但是如果问,你是怎么沟通的,比如How did you talk to her? By phone. 这里就要用by了
也就是说在手机上说话,要用on,但是通过手机怎样,要用by
如果还有问题可以问我~