Sales/ Customer service

I received a call from the call centre wanting to sell me a policy, I told them I was not interested. Since then I have received several calls a day. I have blocked their number but they still keep phoning me several times a day. I sent them an email to state that they must stop phoning me or I will contact you and blast them on social media yesterday and today they are still phoning me. I don't know what else to do as I can't even concentrate at work because my phone rings all day long. The number they use is ********** . Please help.