There could be multiple reasons for your account to be charged even though you are not running a campaign:
1. Rental of numbers: Whether it's the call center number, a texting number, a shortcode, an adaptive texting block, a dynamic caller ID block or a dial-in number. They all have rental charges which can be checked from the numbers page.
2. Phonebook analysis: The phonebook analysis tool also comes with a cost with 0.01$ for each number. The cost of analysis of any phonebook is shown before the analysis.
3. Incoming calls/messages - The incoming calls and messages are changed as per the inbound pricing. Also, after the creation of campaigns, one can send a test message or make a test call, which is chargeable.
4. Verification of numbers: In the numbers section, you can add your own validated number. The verification of them is carried out through a verification call. The credit for them are also deducted from your account.
5. Recording audio: The media section of your account gives the option to record audio & celebrity recording which inturn initiates a call deducting credits from your account.
Well, that's how you can be charged even though you are not running any campaign.
Manage your credits wisely!