I had faced two problems with Wamp.
1) I cannot upgrade the php version. I tried a recommended way https://john-dugan.com/upgrade-php-wamp/ , but it didn't work.
2) I cannot change the php version from 5.6.16 to 7.0.0 (the default versions of wamp)
These problems showed up when I added a Magento framework in my wamp server. The only version which accepted for Magento setup are 5.6.5, 7.0.2, 7.0.4, 7.0.6
What Can I do?
If you are using a version of WAMPServer > 3.0 then there are lots of simple php ADDON installs that you can pick from
See SourceForge repo for all the available PHP ADDONS
Or the backup Repo which can be easier to navigate than SourceForge.
These are simply download and run the installs. It will just add another PHP folder in the usual place in the wamp folder structure.
You can then Switch to the new release and back again to older releases using the wampmanager menus.
Note: There are also many versions of Apache, MySQL and mariaDB as well.
And if you upgrade to WAMPServer 3.0.8 (again a simple download and click the install), you can also add MariaDB installs as well.