Welcome to the community!
It depends on the type of Yak long distance (LD) service. According to Yak,
With the exception of our 10-10 Yak Service, all of our Long Distance plans are compatible with Mobile Phones.
~taken from here.
If you're referring to Yak Per-Minute LD, you should be able to dial the local access number with your mobile phone (Two-stage dialling). You can find your local access number following their dialling instructions. You should note that since your mobile phone is connecting the call, it would be considered airtime (plus LD charges if dialling an access number outside of your outgoing local calling area).
Hope this helps