Hello XXX:
I'm your colleague and my name is XXX.The reason why I'm writing you this letter is because i want to give you some advice.When you are talking on the phone,could you please speak a little bit softly?and also your ringtone is too loud.I don't mean to blame you,but it really distracts my mind,and i can't concentrate on my work.
Thanks for your understanding
Take care
XXX