A lot of issues here. Firstly, call only ads typically get less clicks than expanded text ads. If you are getting a lot of impressions and no clicks, you will want to check your search terms and make sure they match the intent of the traffic that you want. Exclude any searches that do not. Also, 16 clicks and only 3 calls seems also to point to bad traffic, as our call only campaigns typically end up with 50-75% of the clicks resulting in calls. Thirdly, if you are tracking conversions, this allows Google to use a forwarding number if they wish. We have seen in the past that the forwarding numbers can actually route the call to someone other than your client. Many missed calls are also a sign of this.