Can't send or receive texts after porting my old phone number

Hello! 2 weeks ago I have decided to give SMARTY a try and ported my old phone number from Vectone. Since then I can only make and receive phone calls, but can't send or receive SMS text messages. After trying all the guides I could find on the website nothing worked so I contacted support via the live chat. They were extremely unhelpful, asked me the same questions over 3 times now and then leave me waiting. I need to fix this urgently since this is my number that I use for 2FA in all websites and most importantly Universal Credit that I must have access to at all times or could get into very serious trouble! I am using Android 8.1 and would be very thankful for any help on this. Thank you!