Product: Checking or savings account

On XX/XX/XXXX, early am., I attempted to electronically transfer {$5000.00} into my Capital One checking account along with separate transfers into one other bank accounts in anticipation of purchasing a vehicle for my daughter. I was adding to existing funds already in the accounts. 
Later on, XX/XX/year> I purchased a vehicle for my daughter that was a much lower amount than anticipated. I wrote one check for {$3600.00} from the Capitol One Account, I wrote additional checks on {$3000.00} and {$1200.00} from separate checking accounts. We all assumed everything was complete and I drove the vehicle home. 
On XX/XX/XXXX XXXX received a telephone call from the auto dealer I had purchased the vehicle from and was informed the Capital One check for {$3600.00} had been returned for XXXX. Immediately I called Capital One Bank and asked for an explanation. I recalled Capital One several times in an attempt to reach someone that spoke clear and concise XXXX. 
On XX/XX/XXXX I recalled Capital One again and asked to speak with a supervisor. The supervisor told me {$5000.00} transfer from XXXX Bank was not available yet and that the {$3600.00} check and been returned because the account has a balance of $ XXXX. 
On XX/XX/XXXX, PM, I called XXXX XXXX and requested an additional {$700.00} be transferred to my Capital One checking account and that the funds should be made available the same day. 
On XX/XX/XXXX am I called Capital One and the customer service agent from Capital One verified my checking account had a balance of {$8000.00}. The agent further guaranteed that if the customer resubmitted a check for {$3600.00} Capital One would not return the check NSF. The Capital One representative agred to place detailed notes on my Capital One account. The additional {$700.00} was still not available. 
On XX/XX/XXXX I received a call from the auto dealer and he stated the Capital One check I wrote had been returned NSF. The dealer had tried to deposit the check after the guarantee from Capital One. At XXXX pm, I called Capital One again and asked to speak to a supervisor since the agent who answered spoke poor XXXX and did not seem to understand anything. I was transferred to a Capital One representative and attempted to explain my concerns. The agent was rude and continued to interrupt me and talk over me. The agent stated he could see my accounts had $ XXXX available and further stated the check could not be accepted since it was written on XX/XX/XXXX. I tried to explain I had records that {$5000.00} had been deposited into my account but that Capital One had not credited the {$5000.00} to my available funds The agent continued to interrupt me and refused to transfer the telephone call to a manager. The agent stated he was the final authority and there was no else I could speak with. 
XXXX ). Why was the check returned NSF when a Capital One agent, on XX/XX/XXXX, guaranteed the check was be honored. 
XXXX ). Why didnt Capitol One process the {$5000.00}. In a timely manner XXXX ). Why did the Capital One agent refuse to offer any alterative to speaking with an agent who was abusive and disrespectful. Every long-term customer should be the opportunity to pursue a grievance.