Herotel not honouring contractual agreement

When I first signed up, the service was excellent and the fibre line speed as contracted - 50Mbps. However, laterly, the line speed is way below the contracted speed - just tested Ping 7ms, 23.73 Mbps download and 26.96 upload. When I lodge complaints, which has to be e-mailed, the response time is many days. E-mail received stated the following: "Thank you for taking the time to rate our services. We take customer satisfaction seriously and are glad to hear from you. I want you to know that we appreciate your feedback. It will allow us to resolve any problems that occur and help us to improve our services." I suspect automated e-mail.