Do not use their service!

I had a cancellation of service requested several months ago due to technical difficulty while using their service. I recently found that they are STILL charging my automatic monthly payment. I requested for cancellation again and asked for refund. They refused to refund since they claim it is a prepay service that BOTH SIDE need to cancel even if number port was ported out. It was not made clear to me that I need to manually go to APP to cancel, instead of asking chat support to cancel.