No,that phrase only use in face to face.you can say 我要收线了！收线=hang up the phone

personally I wouldn't use this phrase in a telephone situation. It's more of a face-to-face conversation.

no. Actually we just use bye-bye(拜拜）or 再见（zaijian） 我先告辞了 is used in ancient time.

"我先告辭了". 我認為用在當面告別之外. 也可用在聚會尚未結束. 而個人打算先行離開. 電話裡不適當. 主要是因為一人掛. 另一人也斷. 如果數個人在網路聊天. 其中一人說"我先告辭了". 我認為也是可以. 不見得一定要"面對面".

I think bye bye is better on the telephone.