Ive just been through this when Thaiwatsaduk mixed 9 litres of wrong paint.
Had my phone in front of them and showed them to 2 colours we wanted.
Light grey and off white.
We get home and the light grey was correct but the off white was dark grey.
They said they cant change it cause it's already mixed. I said you mixed it wrong not me.
Again showing the colours on my phone asked how the F is this dark grey off white?
They said I have to pay again at ฿2,400 for the off white. Lost it with them again and they come back with, OK we will give you 9 litres of off white but can you pay ฿400 extra and you keep the dark grey?
It all depends on your airline if they'll let you board from your departure country.
This is the issue. If you arrive here and you are declined entry at immigration who pays for the flight out of here? The airline that flew you here then has to cover the cost to fly you back. The airline can also get fined for allowing you to fly here without a return or onward flight.
So, if you do come here and are denied entry (very unlikely) you're not sat in the immigration detention centre waiting for someone to buy you a ticket out of here.
So, if you already have a return or onward flight you go on that at no cost to the airline.
Im from the UK but i returned here 2 weeks ago on a one way ticket from Frankfurt however, I have a Non O visa and a flawless 22 year immigration record.