I have a customer with a 7100 V4.41a. For quite a long time now the manager's husband has been getting calls on his cell phone, and when he answers, there is nobody there. The calls are coming at random times day and night from one of the customer's phone lines which is line 4 on the phone system. There is no speed dial associated with that phone number, I couldn't find any instance of it in any outgoing call logs or voicemail notification. Any ideas where to look next?