I have had a couple of vintage issues show up with corner dings and one cover tear and and the quickest path to a result was a short, calm message that spells out the difference in condition and what would make it right. If the listing photos showed sharp corners and you received a copy with a tear, say that plainly and request either a full refund or a partial that reflects the drop in grade. For a mild bend I have asked for around a quarter back, for a cover tear I have asked for half, and both were accepted because returns cost sellers time and money too.
If you do not hear back soon,, I would not wait longer than a day or two. I would open a case right now and attach photos and a short note then wait twenty four hours and if nothing moves escalate through buyer protection so it is on record. On a tight budget, a partial refund can be the least painful outcome if you can live with the copy, and if not then a prepaid return gets you your funds for another attempt.
For storage in a humid climate, keep your books in an interior room that stays cool and steady, not in an attic, garage, kitchen, or bathroom. Keep them upright with no tight pressure and out of direct sun. Avoid any quick fixes on the tear, even temporary ones, since that can hurt value more than the original damage.