Tax credits help

Hi I desperately need some good advice over tax credits when the new 24 hr rule came in with tax credits I begged my employer for an extra hour as I worked 23 hours they told me that they would pay me for 24 hours and change my contracted hours to 24 and as I already did overtime I could make the overtime up over the year I never thought anything was wrong with this as after reading through tax credits info I just basically had to average 24 hours then last week my friend told me during a conversation she was pretty sure this isn't aloud now I'm worrying myself sick I can't sleep eat anything I worry a lot anyway as I suffer from anxiety I don't no what to do as if assume my employer would not do this if it was wrong.please don't judge me I just need advice

Tax credits help