Written with people moving from Turkey in mind. The Portuguese rules still apply more broadly.
Online Complaint Book
You don't need to be in the store to file a formal complaint. The livroreclamacoes.pt platform allows you to submit complaints digitally against any registered business, including utility providers.
The business has 15 working days to respond. If they don't, or if the response is unsatisfactory, the regulator intervenes. It is often more effective than the physical book for complex issues like internet contracts.