Sipstation, how many do I need?

I am still learning here. How many trunks do I need for 1 phone? Our office will have two phones in the next 6 months but right now we just have one and in the mist of setting up auto attendant. I do want to be able to put line 1 on hold and take another incoming call. Is that two trunk lines? I bought an SG300 phone

If a call comes in and you put it on hold, you are still keeping the call open - the caller is still connected to your system and your system is likely playing music down the line, so the line is in use. If you want to make or receive another call while that is happening, then yes, you need more than one channel on the trunk.

Have an many extensions as you have people (or desks) and as many channels as need simultaneous calls (in either direction)

Don’t bother - he’s not even reading the responses.

huh? I have ready every response. I talked with sipstation and they said I would need two trunks.