I have mentored a number of PhD students who have changed their supervisors. Sadly, this is not uncommon. The most important factor for success as a PhD student is to choose the right supervisor. That is why I recommend students to do significant amounts of research and informational interviewing about their supervisor before they start working together. That means ideally meeting them in person or doing a video call as well as talking to their previous or current PhD students.
If, after making a careful selection and choosing the best supervisor based on your informational interviews, the relationship between you and your supervisor deteriorates for whatever reason to the point that he or she does not provide you with the level of supervision that you require or there are issues with bullying and harassment then I would address these concerns immediately. If the situation persists I would change supervisor without further delay. I would talk to the head of department, explain the situation, and be very firm in requesting a new supervisor. This is very important.
You deserve to have adequate supervision throughout the course of your PhD and it is ultimately your responsibility to ensure this. Problems tend to escalate once the lines between student and Professor break down and the student feels adrift or is not getting adequate feedback. You can lose a lot of time and momentum in this kind of scenario. Don’t worry about the social awkwardness of this situation – it is your right to request a new supervisor should the one you chose prove inadequate. Take action quickly if you find yourself in this situation. It is even better to change university and withdraw in order to find a supervisor you are happy with than to continue in a toxic relationship or if the department does not arrange a new supervisor for you. This is unlikely to happen, however, if you have done the sufficient groundwork and informational interviewing in selecting your supervisor.