Reliance Trends — Exchange of size of shirt denied by store

I had purchased many items from your harda outlet yesterday but one shirt
was oversized so try I had gone to change its size from 44 to 42 but the store people made me wait for 25 min and said this can not be replaced.i am your custumer from quite a long time and regularly purchase from your store.
very disappointed by this behaviour.
please do the needful as early a possible.
Thanks and regards