Unhappy service

I bought a dress , army green , the lady that was assisting me did not remove the that alarm thing on my dress and now i cannot wear it. This has inconvienced me in so many ways. I now have to spend money on transport and go to town and return this dress. Why are we not mindful of these things? What must i then do because i need to wear my dress?why is it that when i walked out the alarm did not ring do this "mistake " would be rectified