I recently tried to use my card to buy something on my phone for £29.99. My card was declined so I used a different card and the payment went through.
A couple minutes later I get a message from a number, the same as my bank's, telling me "you've paid £29.99. if this is true send Y if not true send N" for the declined card. Since that wasn't true and the payment wasn't made on that card I sent N.
After speaking with the bank they told me it was not a legitimate text so they made me cancel my card. But is my phone hacked now that I've responded to the malicious text?