Hawaii permits noncompete agreements.  To be enforceable they must be reasonable as to time, geographic restriction and scope.   Because of Hawaii's unique geographic isolation, judges have remarked that the key is the reasonableness of the geographic restrictions.  For example, a 10 mile limitation may be reasonable in California but may not be reasonable on Oahu because 10 miles would cover just about every place you could work on Oahu.  The time limitation is also subject to a reasonableness standard.   You need to read the exact wording of your noncompete clause to determine if simply contacting your previous customers would be a violation.  A 2 year restriction is probably reasonable depending upon the nature of the field of work.