In my situation I only want them to stop contacting me so I mat write to the DWP and complain about them there, after all they are trying to get paid for work they havent done

Im in a similar situation, I was with ingeus but found myself some self employed work so I signed off and refused to give any information to ingeus as I didnt want them to benefit financially for something they hadnt done. Evetually the phone calls and emails from ingeus susbsided but my wife answered one this morning and so my advisor was able to speak to me. I still refused to give them any information to "update their records" and asked them to stop contacting me, they said they couldnt as they were contracted to do so by the DWP. Is there a way to legally stop them calling me as I now consider this harassment.