Received mysteries text regarding a code send from my own Iphone after using a unprotected public Wifi-hotspot

Today I received a text from my own Iphone number displayed as +28 18 xx xx that I have not written myself. It said I now had a new code thas was xxxx without specifying what for. Just before I got that text I had used a couple of different public wifi-hotspots. Should i be worried? After i searched Google all I could find was that it was a possibility your Iphone can be hacked on Wifi and the other option was that the code I received maybe was from the Verified SecureCode by Visa & Mastercard that I did sign up for a long time ago. If that was the case someone would be trying to use my credit card. If anyone could help me to disclose why i got the text from my own Iphone I would be very grateful.