Disappointed and EXTREMELY Disgusted

On the 13 February 2015 I purchased a pair of Shayna Blk W7 crocs had it for 2 weeks the strap broke I took it back on the 2 March 2015, it was replaced with a new pair. The strap broke on the right foot as well took it back to the store today asked if there was perhaps a problem with the crocs the Cashier says to me \ITS PROBABLY BECAUSE OF YOUR WEIGHT"well what the hell has my weight got to do with it I weigh 79kgs..you don't say these things to customers"