Frustrated... I cant believe this but i purchased 1000 shares of...

Frustrated... I cant believe this but i purchased 1000 shares of stock last year via a broker, chess sponsered and i was issued a SRN....

sold these shares on comsuk a few months later using my SRN at a small profit...so i thought

Three days later i purchased back after a change of mind (FU no 1) and paid a small some of $305 after the cross trade......

Today i notice i dont have these shares on my Comsuk acc, i think , thats strange and give them a call-- they tell me i have oversold, that the order went thru even though i did not have the shares to sell.. how is that possible????? I typed the SRN no in the sell box and it went thru, if SRN not right then it wont process true??
Well comsuk dont agree,i have confirmed the original holding it does exsist and the SRN correct. They took the cross trade diff of $305 + $60 BF for 2 trades and sent me confirmation emails for the trades...i would never had known.......

stupid i know, but i still dont think this is my fault, or is it???comsuk say it is......WTF input please pi**ed off