Trying to give me factory rejects!

I am extremely disappointed with the MTN Featherbrooke. After doing an upgrade on the S6 Edge, I got home and noticed there was an issue with the software. The software refused to update and I kept getting constant pop up error messages. When I took it back 2 hours later, they refused to do a swap and the manager told me software is not covered in 7 day guarantee and I must go to Samsung to do a system upgrade despite me insisting they give me a new phone, how can a phone out the box already need to be taken in for checking? I went to Samsung and they picked up further intermittent issues which I may not have noticed. The regional manager for Samsung told me that they don't do any software upgrades on phones less than 7 days old as the store should automatically give me new one! He then walked me to the MTN branch below his store at clearwater and told the manager to do a swap for me. I am disgusted that MTN Featherbrooke refused to take back a phone 2 hours after I bought it and wanted to pass on their factory rejects to me! The store manager does not care for customers and could have done a better job in resolving my query, he was very dismissive and I will never use that branch