purchased new home which included Viwinco windows ...

purchased new home which included Viwinco windows 7 years ago; the locks on one of the casement windows broke in the lock position and cannot be opened; Viwinco warranties parts for life; the territory sales representative for Viwinco said in was due to excessive force (only my wife and I have lived in the house and no children etc.) and indicated we would have hire a lock smith to open window; we have hired two glass companies to try and open window and it cannot be open without taking entire window out; Viwinco refuses to send out someone to look at window and offer a solution; the warranty covers parts so they should replace the casement window and new lock if only solution is taking window out; very disappointed that we have 7 year old window that doesn't open; any help would be appreciated