Failed Bank Promises

I used online banking forex global payments - "best foreign exchange provider for 5 years running" to transfer money and guess what 6th October 2021 and by 14th &15th I began making follow ups and still nothing, by 18th October money got paid back into my account with the money reduced, no explanation, no nothing. Now I have had to make several follow ups and I am only been told that there is no correspondence bank for which my beneficiary bank uses. my ****es me off about this whole thing is that it had to follow up and my money is cut off.

As a customer, how do I know what happens in the background at the bank? I should have been told day one that that transaction will not go through and not for there is no correspondence bank, now my money is paid back short and I did not achieve my goal... the way the bank handled this has made me very unhappy 🙁