Please help...

Maayung gabii!
Can you please help me? palihug..
what is the difference between the two sentences below
Mopalit ko og saging
Magpalit ko og saging
Both those sentences mean I will buy bananas but when do I use 'mag' and 'mo'?
Salamat po

salamat

Thank you! it makes sense to me now.  BTW, LOVE the sight! It is an AMAZING recourse for my learning of the bisayan language!