I have a right to return staff when ever I feel

I got to their store on Saturday wanting to return their product n this other lady at customer service is telling they can't help me exchange coz I changed the bag during De week. A product I wanted to change wad still as I bog it and I had prove of purchase . The lady went and called his manager who also said De same thing they are not helping me coz I was changing something during the week. <br> <br> They accused me of being in their store of which I was not, even if I was doesn't one have a right to return staff when Eva so long as its still as it was bot and there is a proof of purchase. I left De store very angry and feeling judged.