how to change number to phone

I moved to Lebara and ported my number successfully however the sim card has retained the number the sim card was shipped with before porting. I cannot change the number in my iphone. my husband moved to Lebara as well and his is fine and his old number moved. any tips ?

Have experienced this myself in Android but it doesn't really affect the operation of the phone in my experience as long as my actual number is the one that's sent when making calls etc.