Bad service & returned phone

I called to upgrade my phone to the new Iphone 6S. All went well and I agreed to the adhoc fees for upgrades and the fact that I had to get a nano sim card for this phone which resulted in paying for a sim swop once I received the phone..<br> Phone arrived timeously, wonderful. 3 Days later the phone was not working. Called to report the phone and was told that I had to return the phone and once received they would then reverse all upgrade charges etc and contact me to redo upgrade. Phone collected a week ago friday.Now using old phone and had to buy sim converter. Now receiving an automated call stating that my account is in arrears of R146.00 and that I must state when I will pay this otherwise my acc will be frozen. Customer service says its due to the upgrade going through after my debit order and that I should contact collections to sort this out. Being pushed from pillar to post. Calls wont stop. Have called 3 times to speak to Nadine regarding the upgrade, first time I left a message, no return call, 2nd time didnt bother, today she is on leave after I stated who was calling. Who can sort this? I would like the phone. Corporate policy getting in the way of good service?