電話

電話 = denwa

携帯電話 = keitai denwa (or just keitai)

電話を切る
Denwa o kiru
Hang up the phone

彼の電話番号を覚えているが思い出せない
kare no denwa bangoo o oboete iru ga omoidasenai.
His telephone number is at the tip of my tongue. (舌の先にある = shita no mae ni aru)
(I have remembered but I can't recall)

販売部にご用の方は、＃の後に１を押してください。
hanbaibu ni goyou nohou wa shaabu no ato ni ichi o oshite kudasai.
For the sales department, please press one followed by the pound (sharp) sign.
(*Or: please press the sharp/pound sign after one)