Lost slip , and nappies removed but still cant return

I buy my sons nappies from clicks every month , the jumbo pack of clicks brand nappies and never had a problem with the brand.

Saturday i Bought a pack and when i got home i removed it from the pack and packed it away like always. Yesterday morning my son was soaking wet when he woke up and the one side was completely loose,then i noticed when i changed him that the nappies one side does not stick properly the sticky comes off it is a manufacturers fault.

so i checked the rest of the nappies and saw , that most of the nappies has the same fault.

I then called the branch where i bought it from and explained to them i would want to return it just for another pack,and i did not have the slip they said its ok because they can get it from my clicks card,but when i said the nappies is removed from the pack and i threw the pack away,they said to me i am not allowed to return it because it is removed from the original packaging.

So my thing is i am a loyal customer that spends hundreds every month. i am very disappointed in clicks so now i have to sellotape the side that does not stick.