This will very much depend on the service provider in question. The law relating to goods and services discrimination is civil law, and it is therefore not something the police can take forward. You could:
1. Make a formal complaint directly to the service provider or manager to highlight the discrimination
2. Follow the complaints procedure for the service provider, if there is one in place - institutions like the NHS for example will have a set procedure
3. Contact the relevant regulatory body or Head Office for the service provider, if there is one
4. The service provider may need to be taken to county court to gain redress (which will generally be compensation-based).