Callable Bond being called: Reason why need to buy below par/ callable price

VRXCN@OTC has announced it will become subject to a full call effective 20170815.

7 JUL 2017: bought 4K at 101, 6.75% coupon, next call 100 at 15 AUG 2017.

P/L is around: -101 +100 -commission + coupon =~ (1/2%) in a month.

added one more rule into my list when buying bond:

• price < MIN(par, callable price)