Providing a sole trader ABN will give me a 20% discount compared to the plans available on the website (i guess this is the personal ac).
Are there any drawbacks?
Can I still travel for free between this ABN account SIM and any prepaid yearly deal on the market?"
Makes no difference to your telco freedom, that's simply a telco decision to offer ABN holders a discount, nothing more (#marketing)
I did this with Optus a few years back and it had an impact on my credit score as it was a ‘commercial’ inquiry or similar (in its own category separate from banks etc) rather than a normal one. May be important to you if looking for a loan in the near future.
Which provider? Which plan?