1. Downloading the app to see if it will let you in to change / update it in the settings.
2. Use the forgotten password option several times.
3. Trying another browser that may let you in without phone verification (then change it when you have logged in).
4. Trying again another day when sometimes you can get in without doing the verification and then change the number.
5. Changing the password a few times sometimes works as it can bypass the phone verification.
If that does not work then you would need to contact customer services so that they can i.d. you another way and then add your new phone number to your account.
Contact options for Paypal are accessed by clicking help/contact bottom left of Paypal pages...
1. Paypal phones are slowly re-opening and increasing in numbers (you can use the guest option if you can't log in). 2. Live chat is also randomly available. 3. You can send them a message, during business hours you may also be able to message whilst logged out. Or 4. Have you considered contacting Customer Service via Facebook or Twitter? You can send them a personal message from their Facebook or Twitter pages. It's: https://www.facebook.com/PayPalUK and @AskPayPal for Twitter.
Advice is voluntary. Kudos / Solution appreciated.