Mango Leggings stitching coming Apart

On the 4th of March I purchased MANGO Leggings from Edgars Menlyn and paid R799 for these Leggings. I have worn the Leggings four times and they have been washed once. To my absolute disgust these expensive leggings are falling apart and the elastic looks worn, as though I have had the leggings for years. <br> The Edgars Customer service manager Anzani Marageni, was not very helpful, and I was told that my one wash damaged the pants because I washed it with Jeans. This is absolutely unacceptable. I do not only expect a 100% refund for this inferior quality, but I demand a response from MANGO as to why this quality, which should be outstanding for the price you pay, is anything but desirable. MANGO is supposed to be a reputable brand with international quality, but this has not matched up to my experience.<br> Please respond to me as I am sure this is the least I deserve for wasting my money on such an inferior brand.