Charges Raised for Services Not Rendered

I was engaged in a fix term contract with MTN with regard to my cell phone account. My contract expired on the 5th of February 2015. MTN bluntly de-activated my cell phone number, without any prior warning. It took me seven (7) working days and a lot of phone calls to get the number activated again. When the number was activated again I could only receive phone calls, but could not make any. The worst part is that I use the number for business purposed and now had subsequently suffer a huge loss of income due to the inconsideration of MTN. The cell phone number had since been transferred to a Pre-paid line, to see if the problem could not be sorted out, but one (1) month later and I still cannot make any phone calls. I can only receive them. MTN still has the audacity to deducted the contract line rental fees from my bank account, even thou the contract had expired. The bad thing is that MTN will not allow me to port the number out to another service provider, basically trying to force me to stay with MTN, due to the fact that I use the number for conduct business. I am extremely frustrated and will never, ever engage into any business with MTN again.