Troubleshoot the issue by working through the instructions under
"Membership / Item not added to account"
on the
Common Mobile Payment Issues
support page.
Google Play purchases can take up to 24 hours to be delivered to a Runescape account.
Check that the purchase was made for the correct Runescape account (check any other RS accounts you own).
And the final point is:
If your Google Play payment was definitely successful visit the in-game store and you should receive a prompt to pick up your purchase. Make sure you're logged into the same Google Play account that you made the purchase on.
Also try this:
A few days ago another player reported that, after waiting 24 hours and no Bond, they cancelled the purchase through Google Play and purchased again. The replacement purchase was delivered almost straight away.