All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
All perfect praise be to Allaah Who enabled you to repent before it is too late. You should know that whoever is involved in Ribaa (interest and usury) not knowing that it is forbidden, then he is not sinful but he should repent in any case, and give back the money to its owner. If there is no way to avoid paying the Ribaa, then you should pay it and the sin it in this case is on the one who takes.
For more benefit, please refer to Fataawa 86202 and 85749, and for the conditions of repentance, please refer to Fatwa 87903.
If it is not possible for you to borrow money without Ribaa in order to pay your debts to the bank, and delaying the payments of installments will lead to a monthly deduction from your account, then do not borrow money with Ribaa in order to pay your loan unless you are really in necessity to do so. If such is the case, then we hope that you are not sinful for this monthly deduction as you are excused for not being able to get rid of it.
However, you should try your utmost to get rid of the consequences of this Ribaa which you were involved in. We ask Allaah to help you and accept your repentance.
As regards your second question, it is permissible to change your name or to add or omit some letters from it as long as this does not lead to mocking the named person.
Indeed, Al-Bukhari wrote a chapter entitled: "Whoever, while calling a friend, omits a letter from his name", and he mentioned in it the statement of the Prophet to 'Aa'ishah : ''O 'Aa'ishah, this is Jibreel (angel Gabriel) sending his greetings to you.'' She replied: "Peace and Allaah's Mercy be on him."
Furthermore, the Prophet called Anjashah, the Prophet's servant: ''O Anjash, pull the camels slowly when having ladies on them."
Allaah Knows best.