According to the CMA guidelines, reviews cannot be amended and hirers/owners cannot be asked to modify or remove their feedback.

Hirers are expecting a true account of an RV and experience, so having a few non-5-star reviews is normal. Negative reviews are important for both hirers and owners — not only they help you provide a better service, they also build credibility and authenticity of the review system. 

FAQ - Can I modify my review?