As usually IANAL and I do not know the specifics of the contract you signed then not Lithuanian LAW.
So what will happen if you don´t pay your dues:
First You will get payment reminders, probably loaded with additional fees.
If you still do not pay, the creditor has to decide: Drop the debt, go to legal proceedings or sell off the dept. Most will probably sell the debt to professional debt collectors.
Those will contact you, with even steeper fees an will possibly operate internationally.
This can mean that:
- The money owed (+fees) is seized from your bank account
- A marshal knocks on your door to confiscates valuables
- You are registered in rating systems as someone who does not honor a debt and therefore will have a hard time getting loans, bank accounts, rented property or mobile phone contracts.
It is hard to tell how well this works on an international level, especially without knowing any details of your situation and the country of your residence.
Note that you are not only responsible for the money you owe, but also for the fees and interest those can quickly surpass the original amount of a neglected debt.
So I go with @Davidm176´s recommendation: If you currently can not afford to pay them in full, contact them an try to negotiate a deal.