For changing your mobile number linked to spotify, you would need to login at the spotify website. Just go to www.spotify.com and login to your account.
Once logged in, click on your profile name or profile picture on the top banner of the page, click account, then click profile. From there, you will be able to change the connected mobile # of your spotify account.
I hope this helps and best regards!
change your number on spotify.com
I changed the mobile number registered thru spotify and it still gives me the same error message.
there is no change number in profile then how can i change it?