SIP offer modification

Hello,

I wanted to change our SIP plan but the options presented are a bit confusing.

We are on an old plan that I believe no longer exists (SIP Enterprise – Fixed lines included – 10 mobile hours), and our needs have evolved since then.

When I try to switch plans, I'm shown this:

What is the difference between the SIP Enterprise and SIP Trunk offerings?

Also, is the plan change done transparently? (downtime, IPBX configuration to modify?)