Tire Shop installed lower rated tires,now having problems. What are my options?

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My tire shop (national chain) sold and installed 4 tires on my MPV. Still under warranty, but problems of vibration at certain speeds. Tires also shows premature signs of wear. Another shop said that the tires sold to me are not the speed rated tires for my car per the mfg and is the reason for poor performance. Should be 94H and received a 92T instead.