Once I buy tango premium chat and voice service now I have charged again I didn't give any authorisation ...

If it's this app, Tango, Text, Voice & Video, then it's description page in the store includes :

Try Tango’s Premium Discovery – Chat with the most popular people on Tango

- Available for $9.99 per month

- Payment will be charged to your iTunes Account at confirmation of purchase

- Subscription automatically renews unless auto-renew is turned off at least 24-hours before the end of the current period

- Account will be charged for renewal within 24-hours prior to the end of the current period, & identify the cost of the renewal

- Subscriptions may be managed by the user & auto-renewal may be turned off by going to the user's Account Settings after purchase

- No cancellation of the current subscription is allowed during active subscription period

There are instructions on this page for managing and stopping auto-renewing subscriptions : http://support.apple.com/kb/HT4098