Excuse me, but...

(a)  

Who are you? / Who is this? (polite)

(a)  

Hello (answering phone)

(a)  

phone number

(a)  

cellphone number

(a)  

to send a message

(a)  

to receive a message

(a)  

to receive a call

(a)  

to call/to phone

(a)