whoever sold you the stroller really got no conscience one! she obviously knows about the brakes not working since she is avoidong your call now.
But i think its hard to get compensation. Cos it is our onus to check the item before we buy.
I know how you feel cos i bought a bag from a mummy here earlier this year. Also listed as no defects and when i picked it up, it was below her block and it was dark. I looked thru and brought it home. This bag is from a reputable brand and is supposed to be leather but when i used it the next day, the bag started flaking off everywhere and was unsightly by the end of the day. Upon contact sure flake off one!
Tried calling her and as expected, she didn't pick up . What to do! Wasted $300 on the bag .
Mine case not as bad as yours, its good thing your child was not hurt.