Product: Credit card or prepaid card

Hi Im XXXX XXXX, I would like to submit a complain regarding my Union bank credit card.. 
my bank statement on union bank posted on XX/XX/XXXX to XXXX XXXX cause a difference in my credit score from XXXX score dropped down to XXXX score. 
I decided to pay all my debt on my union bank credit card bill posted bank statement last XX/XX/2020 to XX/XX/2020 and I paid the whole amount the I owe, plus an I overpay of {$94.00}. I called union bank to let them know that I am aware of the an extra {$94.00} that I overpay and I requested a check to be sent to my address so I can redeem my money back that I over pay, but they didnt allow me to do so because of theyre policies, they gave me an option to use a {$94.00} of credit to be used. We both agreed to continue with that option.. 
I purchased XXXX XXXX {$13.00} and it went through, I still have {$80.00} on credit so I order XXXX XXXX and worth {$62.00}, I still have {$18.00} of credit, they accepted the XXXX XXXX purchase but they declined it too and accepted it again and I wasnt able to track what could be the reason of the declined purchase for I have a credit to be used, I went and purchase on XX/XX/XXXX same order through XXXX it declined and in my mind it declined already but after few days it went through.. after the billing cycle ends and after the declined purchased and accepted purchase transaction they didnt not communicate with me what could be the reason of them declining my purchases and accepting it after got declined with no advice of what is going on with my bank transactions, on top of it, I owe them {$1.00} and now that is XXXX I owe them {$8.00} for they put interest charge from {$1.00} now they are claiming that I owe {$8.00}, they did not contact me through my address about what I owe, they didnt send me an email for what I have to pay the {$1.00}, they only give me an option to communicate with them through phone call which I called the number on the Back of my card, and for them to reach me back, specialist that I called from union bank told me that I dont have an option to communicate with them through email.. Union bank gave me a phone call through a No caller ID number which when I receive theyre calls, union bank phone number wont register to my logs for they are calling me through a caller no Id set up, and they ask for  my credit card number information, Social security number, birthdate while they are contacting me through no caller ID number, I told the bank that if they can call me through a non caller ID number for I am not comfortable disclosing my personal information and social security number for a bank that calls me with no number, they didnt give me other ways to contact them too such as emails or mail.. and now Im waiting for a respond of my complain and they say I will expect a phone call and it will still be no caller ID and from the previous phone calls I had with union bank they would not proceed with my concern or help me settle the Payment of {$8.00} without me disclosing the security question such as my name, birthday, address, ss number through no caller Id phone call.. how would I know if its legit the union bank that is calling me and not a scam for it doesnt have a number? Please help me, my goal is to close both of my debit card and credit card account after all this.. thank you so much.. to call me back my number is XXXX