Well, apart from 'shouting' (all capital letters is considered rude in forums such as this), using 18866 to call Spain is a mistake now because their per minute charge of 2p to call Spanish landlines is double what 18185 charge.

OTOH, their 10p rate to call Spanish mobiles is 1p better than 18185 and 5p better than 1899.

18866, 1899 and 18185 all charge 5p connection fee now so it's a question of picking which one to use according to the per minute rate for the destination in question.

I use the MSE site's Callcheckers to find the cheapest ways of making my calls.