"I'm told" generally refers to a rumour or gossip, for example, "I'm told that they are going to fire 20 people", it's fairly synonymous with "I've heard that...".. Whereas, "I've been told", refers to something you have directly been told, sometimes it is followed by a name or pronoun, for example, "I've been told by them/the company that they will be firing 20 people". In the first instance, the information is something that has come to you by indirect means, e.g., someone has mentioned something to you, whereas in the second instance, the information has come to you by direct means, e.g., you have been told.

I am told means it is something you know of generally. Like a common idea or common opinion. I have been told, means someone told this to you in the past and the information is relevant now. "I am told Budapest is a beautiful city" You hear this quite commonly. "I have been told to go to my exam tomorrow" One specific person gave me the instruction and it is important at the moment.