Two failed tickets (xxxxxx and xxxxxx) to Köln Hbf from Singen Hbf on 1/07/2019

On July 1st, I bought two tickets(xxxxxx and xxxxxx) to Köln Hbf from Singen Hbf through DB navigator app. After I bought the first ticket, the app showed "journey cancelled" immediately. So, I bought the second ticket and when the purchase was finished, it said the partial journey to Stuttgart Hbf was cancelled again. And finally, I bought ticket from the DB machine and still was not sure about the journey so I went to the DB office and they changed my ticket that started my journey an hour later. So, can I get refund of the two tickets that I bought online? They have already deducted amount from my bank account. Please Help!

[Edit by community staff, 07/10/19, 06:03 a..m.: personal data removed.]