I agree with Bill that they do technically have very slight nuance differences between them but, as he also mentioned, no one would really worry about using them so precisely anymore; in fact, I would say that "I was ON a call" is by far the most commonly used in all situations nowadays. Bill also said that "both are good right?" doesn't sound natural but for me it is a very common contemporary casual expression.

Thank you !!!

Agree with Bill. I always say "on a call". It's simpler and sounds more natural.

Yes, both are correct but they mean slightly different things dependant on usage. Being in a call suggests something like a conference call (multiple people), while on a call suggests one to one. But for many people these differences do not exist. both are good right? A bit odd. I would use, are both correct?