Opodo complaint: Mis-sold services

Purchased a flexible ticket to fly on the 10th of October from Manchester airport to Douala Cameroon through Opodo. Realised that my planned travel was not going to be possible , so l asked the sales representatives at Opodo to change my ticket.Well l was told that a request to change was sent immediately and have to give them 48hrs.After that time elapsed l called and it seemed as if they were not aware of this issue as l was told that it will take a further 24hrs and this time l will be able to get positive results. They told me that l will either receive a call or an email stating the outcome.That did not happen so l called l again .l did not seem to be getting thus issue resolved at all.Well assurance was given again this time but no positive results .After all this l received an email saying that my ticket cannot be refunded nor changed.l was surprised by these developments. Called again and they told me that they are going to send a request of the date change.So l concluded that all this time l have been calling and was told a request was sent that was not true. Because prior to that after l had called to change the date .l received a flight ation from the airline and them stating that ,l was travelling the same dates l had previously said l won’t be able to travel .So after waiting for 4days my issue was not solved and was told to fill in a claim form.l was really disappointed because, l paid extra money which l thought that it will allow me to make changes,and was told that what l paid for was gonna be possible. I knew that the flexible ticket allowed me to change the ticket and will pay the difference in fare price.