127 complaints by customers were upheld by the Financial Services and Pensions watchdog in 2018.
The office has published a list of cases where compensation was awarded.
The FSPO's job is to try and resolve a complaint or dispute when mediation efforts haven't worked with a financial service or pension provider.
In 2018, 234 legally binding decisions were made, and 127 of them were either fully, substantially or partially upheld.
They have the power to instruct a provider to award compensation of up to €500,000.
Last year, a couple whose mortgage provider "adopted an obstructive approach" after they fell into arrears with a buy-to-let mortgage received compensation of €90,000.
€3,750 in compensation was awarded to a customer whose bank opened a new account without her consent or knowledge.
Another case saw a driver awarded €3,000 after he lost his no claims bonus having reported a crash caused by an uninsured driver.
One woman received €250 after her travel insurance policy automatically renewed and she was refused a refund when she went to cancel the policy.
Ombudsman Ger Deering said it's clear from the decisions revealed today that some providers don't always act in the best interests of their customers.
He said: "I have found that it is still the case that some providers are not willing to listen to or engage sufficiently with their customers in order to resolve disputes.
"Where disputes are not resolved by agreement, I will continue to use the extensive powers available to me to investigate and adjudicate complaints in a transparent and impartial manner to ensure fairness and, where necessary, to direct providers to pay compensation or rectify their conduct”.
The legally binding decisions have been published on the FSPO website.
Reporting by Stephen Murphy and Stephen McNeice