Cat6e to RJ11 - Known methods for landline phone systems.

We're building out a new office and I've instructed our IT sub to put Cat6e everywhere, which they have so we can use a new VOIP phone system with our two phone numbers and 7 handsets. Unbeknown to me at the time, but most VOIP providers charge per handset, not per number like our current traditional phone system. We obviously don't want to pay for 7 users as we only have 3 employees in the office (we're future proofing), so we're in a situation that I'm not sure how to move forward. I've looking into RJ45 to RJ11 converters, but am getting mixed reviews. Can we use our existing Cat6e cables to facilitate our current phone system and not use VOIP? We're only paying for 2 lines and that's how we'd like to keep it at the new office. Thank you!