R2700 for migration????

I recently got migrated from a open line contract to a top up contract which I had requested since I opened up the contract in December 2014. I was told that migrating to top up would cost me just over a R1000 I called Cell C to query my bill today they told me R2700 now I know my monthly bill is R700 on top up. But charging me R2000 to migrate is obsurd an day light ******* it's appalling to think this is what Cell C is doing to their customers. Looking back now I wish I stayed with vodacom. Cell C advertises cheapest rates what I lie I intend on talking this further