Can a C7100v be setup as an access point?

> I need to upgrade my modem to be able to use 1g speed and I currently
> have a c7100v , [...]

   A Cxxxx model is a modem+router, not a simple modem.

> [...] and one of the compatible modems listed that support the 1g
> speed is the CM1150v, but it lacks wifi for some reason.

   A CMxxxx model is a modem (only). It lacks all router functionality.

> [...] making the c7100v an access point seems too.

   Nope.  You could do that, but you'd still need a router.  Sadly,
without an Ethernet WAN/Internet port, a Cxxxx model can be used as a
modem+router, but not as a plain-old router (with another modem).

   Now you know one good reason to avoid cable modem+router combination
units.

> [...] or would i have to buy another router ? [...]

   Yup.

> ps. the voice capablity is something i need as well.

   I know nothing, but I'd guess that the "V" on the modem model number
would cover that part.

   If you get a router (with an Ethernet WAN/Internet port), and you're
still interested in configuring your C7100V as a wireless access point,
then see, for example:

      https://community.netgear.com/t5/x/x/m-p/1463500

That's written for a Netgear C6300-as-WAP, but the steps are about the
same for any other router (any make/model) which lacks a one-step WAP
option.  (I'd expect a C7100V to be very similar.)