Response of the brand
Thank you for taking the time to review this pump. What can really help with presta compatibility is to screw on a presta to schrader adapter to the presta valve. Some stores often have these lying about so it may be worth asking for one as it will allow you to go up to higher pressures. Personally, I prefer the traditional "track pump" with a handle as it allows the user to reach higher pressures at a faster rate and with less effort, especially for road bikes.
Irrespective of the lack of a receipt, drop a line to your local store as I'm sure they will swap it for you with little fuss.
Regards,
Peter, Cycling Manager, DECATHLON