We cannot charge the account if the user didn’t allow that by adding his/her/theirs billing details and choosing a Premium plan. If you suspect, your account was compromised, do the following:
Change your password immediately. Use this link to reset it.
Choose strong and unique new password. If your potentially compromised Linguix password was used somewhere else, rest credentials for those services as well.
Contact your financial institution. Let your bank know about possible fraud, so that they could react ASAP.