Unexplained Billing and Locking of Phone

I have been a Vodacom customer for the last 20 years. I am using my device for business, and have had endless trouble with Vodacom for the last few weeks regarding my billing. My cell phone contract was upgraded 2 weeks ago, and I now have a bill for nearly R 10 000.00 that Vodacom cannot explain to me... and my device has been locked which is affecting my business. I have always paid my account on time, I received a statement today that makes no sense to me, as from an average of R 700.00 usage per month, I have been billed an average of R 2 000.00 per month for 5 months... I have queried and nobody is able to explain what has gone wrong... to me, the biggest difficulty, is my device being locked, which contributes to me losing business... if this query is not resolved immediately, I will be invoicing Vodacom for loss of business due to me not being able to utilise my device... the second biggest difficulty, is the 5 months incorrect billing to be resolved, in order for me to settle what is CORRECTLY outstanding... I refuse to accept charges that I am not responsible for, especially when nobody can explain what is going on!!! I have spent more time on the phone with Vodacom trying to resolve this, which also has resulted in wasted time and loss of business, which I should be invoicing Vodacom for... If this is not resolved TODAY and my phone unlocked and my billing investigated, I will personally be coming through to your offices in Midrand and will not leave until this is resolved... you can decide how you would like to deal with this!