When an account is hacked, it may be locked for a few days while UA confirms that the account holder was not involved. But, given that this is a month old, you should presume that UA believes that you were somehow involved OR UA's investigation suggests that you may have been involved in other violations of the t&c.
Please understand that nobody here can know what you did or did not do and thus nobody has accused you of wrong doing. Simply that UA likely believes that it has something.
If you search FT, you will find that none of the customer service channels are authorized to deal with you. Calling, emailing, Twitter and the like are useless and will generate either nothing or "someone will respond." The fact is that UA will respond when its investigation is complete and it has made findings. Either your account will be unlocked and you will receive a note apologizing for "any inconvenience" or the account will be zeroed out and closed and you will be barred from MP. In the meantime, stop reaching out to UA. It will not help you.
One area for you to consider is not whether you yourself have committed fraud, but whether there is any other person who has access to your MP account. If UA is seeing logins from other IP addresses at roughly the same time as you may have been logging in, that would be something of concern and a violation of its t&c.