Who called from 4256858982

caller ID stated Washington call,  I did not answer.

when i answered no body there, i think it's a robo call to find out if it's a phone or fax

Tried to call back, said number was no longer in service, 5 minutes later.

Received 3 calls from this number this morning.   Tried to call the number back and was notified that the number was no longer in service.

This phone number has been calling our place of business and hanging up. Phone search says it in not a valid number. If anyone knows what is going on, who this is... please advise. Thank you.