Do you have to stick to just one personal trainer?

If either trainer is really busy and they are agreeable, you could use one for cardio/hiit and the other for strength. You have found good qualities with both of them, just a different workout and style. It is something to think about. You could ask, the worst that could happen is that they say no. You are paying them for their service, they are not paying you.

This is just a thought, I have only engaged a personal trainer for 4 sessions to create a workout that I could do on my own in my home so I don't know a lot about ongoing training.

"no one can serve two masters"

She must quest for the one personal trainer that rules them all!

I would just talk to them and let them know what you want to do. Personal training is about you and what you want with the guidance of a trainer.

It seems more concerning to me that you seem to have difficulty contacting them at times? Or did I read that incorrectly?

Depends.

Are you going for "workouts" or you going for actual training/coaching and a program with long term goals?

Most trainers at typical gyms don't have programs- they just dole out workouts that are tailored to you rather than a full long term program. If you are going for long term program- no don't switch.

But if you are just going for the trainer to give you workouts- they can work around each other.

Well said. I completely agree.

After seeing Trainer B he seems very good and more technical focused on the correct form (not that my other one doesn't) this one just does it more and a more strength I used o other machines my other trainer doesn't use with me. He already knew my previous plan was from Trainer A I just told him what I'd be doing an he fixed up a plan which seemed very good just different from Trainer A. His ones are more HIIT an the other seemed more strength conditioning. I feel like I learned a lot from Trainer B thinking it might not be a bad idea to switch between the two an it helps me become more knowledgeable and as they both have their different strengths.

You said it yourself. They both have different strengths, and you can learn different things from each. Limiting yourself to one teacher or way of doing things, especially before you have developed expertise about the exercises and how they work for you, seems like a mistake to me. I'd be honest with both instructors that you are working with both. And at least for now, I'd suggest one be primary in terms of a plan, so you're not being jerked back and forth. If one of them has a problem with the fact that you're also planning to work with other instructors and try different exercises, that trainer better give a good reason -- if the reason seems reasonable to you, and you want to pick that instructor over everyone else, go for it.
I go to yoga classes with a variety of instructors -- some focus on form, some on flow, some on breathing, some on holding positions for extended periods of time, some "push" harder and some are more motivating. I learn something from each and can apply it to other classes. The instructors also take courses from each other. And I've gotten good comments -- like one instructor who noticed especially good form -- that I'd learned from another.
Similarly in other areas of work and home, I hire different people for the things they do best. Even if there were one person who was best at everything, sometimes it's good to have a back-up. Like you found when trainer A wasn't available, and you wanted to keep on track.