Go to your Cpanel and scroll down to Select PHP versions , here you can change your PHP version , or change your available plugins for your account.
MySQLi support from CPanel
By default it must be checked for your hosting ( depends on the version of PHP you are using ) , you can enable or disable this by visiting CPanel and then PHP Version link.
These changes can be done for shared hosting also ( without contacting your hosting support )
If you are using mysqli ( not Mysql ) then you need to use nd_mysqli . This is required as several functions like mysqli_fetch_all , get_result() etc are not going to work without support of nd_mysqli.
You need to uncheck mysqli ( remove ) and check nd_mysqli , you can’t make both checked as there will be a conflict.
Here is the screenshot to make MySQLnd work.
Part of the PHPinfo() showing about mysql