Just to make sure we're clear on what you mean by multilink, are you referring to the use of two modems to "bundle" the separate data pipes together into one? I have spent hours in the past researching this and what I have learned is that modems in this type of setup need to connect directly to modems on the "far end" which are configured for multilinking. Data devices connect directly to VZW's network, and that network doesn't support multilinking. The receiving modem is inside the cell site.
IF you had dial-up modems on a far end which were capable of multilinking, a data device wouldn't be able to dial directly into them as the data device isn't a real v.34 (an example) modem so they would not be able to negotiate a connection.