Disgusting Service and Attitude

In July 2014 they came out to repair my garage door and wall control panel. They removed the wall panel and never returned it. Rentia continued to send me accounts despite me explaining the situation to her. I sent mails which she never responded to. Then on 13 March 2015 she threatened me with legal action. When I called her she again threatened me and verbally abused me accusing me of not getting my story straight. She then sent another threatening email to my husband. I have now had to contact Eugene from the company who has promised to return my wall panel on 16 March 2015. I have kept all her correspondence as proof of her disgusting customer service. I suppose I can open a case of theft against her?