Unfortunately, one of worst aspects of VM's installation processes is that there is no consistency in how the installation is (mis)managed when it deviates from the expected schedule. You may get installed and working on Monday or you may be in for a long wait. No one (including VM) can give you any information that you can truly rely on.
Having a data SIM on a rolling monthly contract is a useful standby in case it looks like your installation is going to drag on.
If you look through the 'Quick Start' forum for similar past topics (there are hundreds of them by now, I imagine) you will get a good idea of how VM behaves in such circumstances.