villain was unknown but looked donkish over 17 hands. Do you guys often call these river bets given good pot odds? what else can i do to contest the pot with medium strength hands OOP?
PokerStars No-Limit Hold'em, $1.00 BB (9 handed) - Poker-Stars Converter Tool from FlopTurnRiver.com

SB ($92.40)
Hero (BB) ($100)
UTG ($101.50)
UTG+1 ($112.50)
MP1 ($142)
MP2 ($102.70)
MP3 ($99.10)
CO ($95.75)
Button ($106.95)

Preflop: Hero is BB with 7, 7
1 fold, UTG+1 calls $1, 3 folds, CO raises to $5, Button calls $5, 1 fold, Hero calls $4, UTG+1 calls $4

Flop: ($20.50) 2, 5, 2 (4 players)
Hero checks, UTG+1 checks, CO bets $6, 1 fold, Hero calls $6, UTG+1 calls $6

Turn: ($38.50) 6 (3 players)
Hero checks, UTG+1 checks, CO checks

River: ($38.50) 10 (3 players)
Hero checks, UTG+1 bets $10, 1 fold, Hero ?