I was put the wrong contract

After both my contracts finished I requested to be on a sim only for both of them. I didn't take a device and specifically for sim only contracts. Now after a year I want to migrate to a higher sim only package and they said I must pay a migration fee, after I queried this I found out that they never put me on a sim only contract, they only put me on a normal contract without a device??? They failed to explained to me that this was different than a sim only contract. I remember repeatedly using the phrase \sim only"when doing the change! And I was 100% sure that I have a sim only deal"