Morata signed for Milan last summer from Atletico Madrid on a four-year contract but was sent on a year-long loan in February to Galatasaray until January 2026.
The former Juventus and Real Madrid striker said he also had to forego other contractual rights he had earned through his work, adding the figure Galatasaray published in their statement was not accurate.
“For me, in life and in work, there are principles that should never be broken, such as respect for each person’s rights,” added Morata.
“Failing to recognise and compensate what has been earned is, to me, unacceptable and contrary to the values of fairness and professionalism I believe in.
“I know these matters are often not spoken about openly, but I believe it is right to give the fans the real explanation of what happened.”
BBC Sport has asked Galatasaray for comment.
Como finished 10th in Serie A last season in what was their first top-flight campaign for 21 years.
“Playing against them, I was able to appreciate the team and the project – you can see that there is a lot of ambition,” Morata added
“I promise the fans and the club that I will give 200% in every training session and every match. I can’t wait to wear this shirt.”
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