Rain network

Rain , the telecommunications company whom I've been with for years, have always been up to date with all my payments however I'm trying to cancel my 4g sim and it seems like Rain is holding me back. No replies to messages the app cancellation process is always unsuccessful it's totally ridiculous. The debit will go off early this month and I haven't even used the network for a few days now. Really disappointed in them . I want to cancel as soon as possible.