Incompetence when migrating service

In June 2015 I was contacted by TELKOM mobile to subscribe to a new LTE uncapped service. I agreed to do this under the condition that they would simply upgrade my existing 10+10 GB service to the uncapped LTE service. Renzo Zanetti from TELKOM agreed to this in writing. When I received the LTE uncapped service in July 2015, TELKOM simply added this new service and kept on billing me for 2 services. Ever since then I have been trying to rectify their mistake, by visiting their offices, multiple calls to customer care and so on. Everytime something is promised but no one calls back and nothing gets done. I need the original service cancelled and past payments from August 205 credited back to my account. I never wanted 2 services and do not need 2 services