Misleading increase fee disguised as an advert

On the the 02 February 2016 i noticed that my debit order for Planet fitness returned unpaid as they have increased my premium. Upon calling the call centre agent to find out why was my premium increased without notification i was advised that she didnt know. i therefore requested that they re-debit my account with the old premium as i was not aware then cancel my membership since my 24 month contract has lapsed in December anyway. She refused and told me i would be handed over if i didnt pay the new premium. i therefore demanded to speak to a manager. i held on the phone for 15 minutes then eventually Lungi attended to my complaint. He advised that i was alerted of the premium under the email sent on the 30th of November 2015 with a heading \ Bring a friend to train free during December.\" I find Planet fitness being misleading and they refuse to cancel my contract without a double debit."