I got a call from this number and they left a message. It sounded like and old lady and she was calling who she thought was her grandson. I tried calling back but immediately got a dial tone

when this number comes up on my phone, it's my Avon Rep.

It was just a random rude person who dialled a wrong number and who happens to use Distributel for his long-distance.

Who owns this number and why did he/she called. I tried to return the call but impossibe.

hung up without replying when I answered

This number is simply a system access number for Distributel Long Distance.  It could be anyone from the Kitchener/Waterloo area who is a Distributel Long Distance Plan customer.