DSL and 2-line phones

["Splat" <spamspamspamspamspaaaaaam!>]

We have two 2-line phones in our office, each on their own cable. Either
phone can obviously utilize either line-1 or line-2. We just got DSL
activated today on one of the lines. Now, I'm not new to computers or
networking but I am new to DSL.

I cannot get the DSL to work. I assume this is because DSL requires its own
line. Are there special 2-line adapters or filters that allows the DSL to
work over one of the lines? I called Verizon tech support twice and spoke to
two different people but, surprise!, said they didn't know. Thanks.
--
Splat