Stopping of Services

I have been a customer of Meo from year 2020 . In the year 2023 I changed the service from MEO to NOS. NOS had written to MEO to cancel my existing service as I was shifting to NOS. I noticed that I was being charged by MEO though request was sent in the month of April 2023 to Cancel the service. NOS had send them the communication via fax . The fax was received however there was no action from MEO end. 

When I went to the store in Almada Forum to bring the point of being over charged they refused and said they did not get any communication from NOS. Upon going to NOS they showed me the communication which was faxed. When I took the proof of communication to MEO they could not first understand the number and then they traced and said it has been sent to their MEO office. When I inquired why no aciton was taken he said that your NIF and NIF of company are different. 

I said that all other information such as compnay name , Company Address , My name and Account no ,are all same why there was no reply and they have been charging me Euro 46.49 from April to date. Which is now 6 months . They are not willing to accept their mistake and have said nothing can be done. I want to know where else can I write so that my request can be looked into.