I will share a little personal experience with you that I had this past year. Last March, I purchased a crystal surfaced call from Andy Kaiser and I hunted with that call during the WV season. Well during July I pulled it out to play on it a while and noticed it was cracked all the way across. I sent it back to him and he replaced the cracked crystal with a brand new piece of crystal and after having it back for 2 days it had cracked again. I sent it back to him and we decided having another cracked crystal wasn't worth the time or the postage so he scrapped the whole pot and made me a brand new pot with bronze glass instead of crystal. I hope that the call wont crack this summer, but I bought a dehumidifier to help remove moisture so we'll see.
Point is if you contact the maker of your call that call maker should replace or repair your call if they are worth their salt. Customer service is what sells calls.