What does your My 48 page say about your current membership status, expiry date and text allowance balance?
Could you have sent 10 very long texts?
Your allowance is measured in individual SMS messages but long texts can use up more than one of these - especially if using accented/extended characters (e.g. texting in a foreign language with accents/diacriticals etc.).
Are you sure that your recently purchased membership has activated?
Or could you still be on an older membership which has not yet expired but whose text allowance you have used up?
In that case you need a text add-on rather than a new membership in order to be able to send further texts until the current membership eventually expires.
Hope this helps.
That's odd - if there was a mistake (e.g. your new membership started but you did not get the required text allowance) then 48 support should be able to explain and fix that for you.