The mere acquisition of a discarded telephone number by your former employer is not in and of itself improper from a civil or criminal nature. However, usurping contacts of clients of your former employer through the telephone number that you acquired to directly compete with him or her could be defined as an unfair business or trade practice under your state's statutes on the subject.The facts that you have written about are in the "grey" area with respct to what you have done is improper or not. There is nothing improper for a client of your former employer to contact you about doing work for him or her. You did legally obtain the telephone number that you have written about, however the clients calling on this number most likely are calling with the intent of contacting your former employer, not you about providing services.