Voicemail on a Dual Sim

I have a dual sim iPhone11. One line is my Personal and the other is my business. I recently forwarded our office phone to my business number. However, when those calls come in and go to voicemail, they are all going to my personal. I've selected my business line to "always use" with that forwarding number and they are still going to personal. Any ideas what I don't have set up correctly? Appreciate any/all advice. Thanks. PS...my personal line is through Verizon and my business line is through AT&T. Would that impact it all?