There are several challenges you may face while negative reviews have been fixed up for your business. Simply by saying that the user which commented negative reviews for your business is not your customer, Google is never going to remove those users. They don’t find it an acceptable reason to remove the comments. In most of the cases, it is really difficult to trace the identity of any user online.
While this is not a compulsory phenomenon that the user who is leaving the review for your business or products need not to be your customer. They just need to have customer experience which may comprise of the fact that the user has contacted you by call or visited you. So, tracing these customers become difficult for business professionals.
Apart from that, companies are under slight risk with these negative reviews. Generally, a viewer, user or you can say audience, would love to have a look at your products and services based on the reviews. While positive reviews will help them have trust in your products and services, negative reviews can ruin your brand reputation.