But IMF's most recent review suggests that there was no surplus: Greece had been counting privatization revenue (ie: the sale of utilities, ports, and airports) --- which they technically weren't supposed to, and those revenues turned out lower than Greece had projected. Further, Greece had accumulated additional liabilities from pensions and tax refunds than they'd apparently stated when they announced their surplus.
If you're not running a primary surplus, it's hard to see how you're paying loans without external assistance. Can you help me understand that claim a bit better?