The creaking of your frame is not a warranty issue and is down to maintenance of your travel system.
 You can use a 3 in 1 silicone spray such as WD40 to prevent this.
Clean your system first using a damp cloth.
 Lubricate all joints including shopping basket frame and wheel joints and leave for a few hours or overnight.
Cleaning should be done regularly to maintain the working of your travel system.