I’ve been charged £10.99, (possibly monthly!) for my Amazon Music App Ikon?

I’ve been an Amazon Prime Member for many years & as a Prime Member we get FREE Amazon Music without limit, access or any charge whatsoever.

However, suddenly this last month, I’ve been charged what maybe monthly, £10.99 for the Amazon Music App Ikon on my iPhone by iTunes!!!

I really don’t understand why this charge has been made?