How does one extend a 4 Awg copper cable?

Hi Reddit Electricians,

I moved into a house recently which has a 4 gauge copper cable left unterminated hanging on the ceiling for an EV charger.

Problem is the cable is too short to continue running it into the spot I want to place the 48 amp charger.

Is it possible to extend the cable or does a whole new cable need to be run?

If it can be extended what product is used to extend ?

Thanks for any advice. I called one electrician and he quoted me 2000 dollars stating cables can’t be extended.

Edit: sorry I forgot to mention I am in the US.