1lt vacuum flask

A vacuum 1lt stainless steel flask was purchased from osmans phoenix plaza in February 2023 , after 2 months of using it ,it doesn't keep the water hot anymore, when contacted the store the manager ishaan states that the law is 7 to 10 days policy and after that they cannot return or refund the item , when asked where does it state that as you have no ts and cs on ur till slip all he could say was I'm sorry mam but our head office rules are those and we cannot return it .