You got scammed, but it says shipping is 1-3 months, so who knows if they actually have stock (doubt it) or they just buy direct from GoPro.

If you have a Hero7, why are you buying this filter? Based on what I've seen and experienced, it's not necessary at all and and minor tweaks in WB and colour that might be needed (usually only if you're free diving down to 20' or further), can be done in post in about 5 minutes.