Looking on the internet deeply has found these results:

I will get back to you is the most popular phrase on the web.

I will be back to you 119,200,000 results on the web	I will get back to you 122,200,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
It doesn't look like this phrase is very popular! The search could not find any examples on the internet.	However, I will get back to you with further information, if you do not mind, Mrs Doyle, and I apologise for not being able to give you a more precise response. I will get back to you on the detail when I have had a chance to study the matter. I will get back to you very soon. I will get back to you with the name you wanted shortly. Let me check the details and I will get back to you with the results of my enquiries. There is an issue; it needs to be looked at, it is being looked at, and I will get back to you as soon as possible. I will get back to you on all of this later. Well, I got to be somewhere, but I will get back to you.

I will be back to you

119,200,000 results on the web

I will get back to you

122,200,000 results on the web

More popular!

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

However, I will get back to you with further information, if you do not mind, Mrs Doyle, and I apologise for not being able to give you a more precise response.
I will get back to you on the detail when I have had a chance to study the matter.
I will get back to you very soon.
I will get back to you with the name you wanted shortly.
Let me check the details and I will get back to you with the results of my enquiries.
There is an issue; it needs to be looked at, it is being looked at, and I will get back to you as soon as possible.
I will get back to you on all of this later.
Well, I got to be somewhere, but I will get back to you.