Two ways, both of which work immediately and both of which cover every campaign we run.
Hit reply on anything we sent you and write the word unsubscribe. Nothing else is needed and you do not have to explain yourself.
Send an empty message to unsubscribe@qspcrew.com from the address you want removed. Your mail program may also show an unsubscribe button at the top of our messages, which does the same thing.
The address goes onto our blocked list and stays there. It is checked before anything is sent, so no later campaign can reach it, and the block is never lifted.
If a message still arrives after that, it is a fault and we want to know. Write to support@qsphq.com.