Billed for a service that I did not subscribe for

I have a ben telkom client since 2015. I had 3 contracts of which 2 ended in December 2019 and one is supposed to end now in February. I received an sms in December stating that I was going to billed for something that I apparently signed up for in June 2019. I then contacted the call centre and was advised that I signed to a service owned by a company called BIGO TECHNOLOGY PTE and I was instructed to pay R2800. I have contacted Telkom incessantly disputing this and they still continue to bill me. Please escalate this as I will not pay for a service I do not know.