Persistent calls from Auto Trace

I received a 'Private Number' call from Auto Trace asking if I had a tracker on my car. I indicated that I wasn't interested, but the consultant continued trying to sell me the product. I cut the call. I subsequently received 7 more calls from a 'Private Number' which I ignored. I also received an sms between the calls, from Auto Trace, thanking me for my interest in the product!!! This is harassment!!! Not interested means not interested!!!