Go out of the Perelik towards the Murgavets through the lounge bar, down the stairs by the swimming pool, and under the passage (tunnel) as you come out the internet/ telephone booths are within a shop front on the right - its about the first shop you come to, next door is a rossignol ski shop, I had 30 minutes for 1 Lev, but got kicked out because they close at 9pm. Very cheap