I don't know how to do to prevent being blacklisted from journals. I wanted to give a talk at an international conference (and not to publish this work as a conference paper). I did not know that it is unethical to apply the same talk abstract for two conferences at the same time (I did submit the corresponding paper for publication to just one journal).
The conference A wanted the participant to register via emailing to a professor who handles this conference. It is the form with details and abstract I would like to give. I sent this form by email as mentioned, and did not receive any acknowledgement or response from him for around 10 days. At almost the same time, I made a contact to the conference B to ask questions about registration. My advisor told me that it is uncommon to pay the fee before a review so I asked them about this.
Then, 10 days later, I made the follow-up contacts to both the conferences. Only, conference B answered me (within a day) and they told me to send abstract and some details to them to review before paying the fee if suitable. Then, I prepared and sent the documents (based on the same paper) to conference B and they accepted my talk. I did not know until recently that we shouldn't apply 2 conferences altogether. I did not receive any response from conference A so is this still a bad practice? How can I do now to prevent being blacklisted? I am so nervous.