Troublesome collegue!

I don't know when i am the only one have to stay in my department, this situation happen to me.
Last week a collegue from another department came to see this troublesome guy but he's not here. She followed me to make a phone call by using my phone. i didn't know anything. so, i allowed her to come. I dialed up and he answered the phone.

Lady: Hey! It's me. How could you do this to me. i was too kind to you till you did this? I won't be kind anymore. RETURN my money!!

(She kept talking about this and blah~~blah) I was a bit stunned and had no idea how could this guy in debt coz he went to the company by bus, got only a child (in public school) and nothing i could said that he could be in debt.

Lady finished phone call and told me that he lent her $$ for half year and haven't returned it.

I don't want to talk about this topic, if this situation doesn't happen again.
Someone calls him again but he's not here. I pick up the phone and a lady (another lady not the same as above) call him.
Lady: Is Mr.M in?
Be: NO! he's out and he'll be back at the end of this month. Is there anything i can help?
Lady: It's personal matter, Can i know your name?
Be: (a bit surprise) Yes, I'm Onkamol.
Lady: When will he be back?
Be: At the end of this month.
Lady: OK. Bye

just 10 mins passed that lady called again

Lady: Hi, Onkamol.
Be: Yes
Lady: I tried to call Mr.M for thousand times but he don't pick up my phone.
Be: .......
Lady: He leny my money for 2 years and haven't returned.
Be: Err.....
Lady: Can i leave a note for him?
Be: Yes.
Lady: Tell him that if he want to alive, return my money
Be: Err... Yes (SHOCK!)

I can't write that kind of message to him. so i change it to "Ms.P Called you about money you borrowed her"

Haiz troublesome!! i don't want to pick up his phone again!!