Incorrect Billing

When I signed a "special" package with Planet Fitness they explained to me that the amount will be R199 a month with every 4th month a double billing (R400)

I went through my statements and saw the following: Jun 2017 - R199 Jul 2017 - R199 Aug 2017 - R199 Sep 2017 - R199 Oct 2017 - R199 Nov 2017 - R399 + R219 = R618 Dec 2017 - R264 + R399 + R399 = R1062

Please contact me asap regarding this