What should I do if have been exposed to someone with COVID-19 and have received a SMS message but also have recovered from COVID-19 and have been vaccinated according to the full vaccination schedule more than 120 days ago and I have not received a booster shot?

YOU ARE NOT REQUIRED TO SELF-ISOLATE.
A person is considered to have received a booster shot if he or she has been vaccinated according to the full COVID-19 vaccination schedule and has recovered from COVID-19 when diagnosis was confirmed by a positive laboratory PCR test for SARS-CoV-2. (regardless of the sequence of vaccination and recovery (or vaccine doses and recovery).

Before terminating your self-isolation, the NPHC has to verify the facts of vaccination and recovery, therefore,  please submit the following information at e-mail [email protected] (you are not required to self-isolate while waiting for the response):
•    Name, surname,
•    Personal identity  code,
•    Telephone number at which you have received the SMS message,
•    PLEASE ATTACH a document proving vaccination and recovery, e.g. EU digital COVID certificate.  
NOTE. The National Certificate or a paper-card received after vaccination IS NOT ACCEPTED.

It is recommended to take a PCR test no earlier than on the 3rd day after contact (except of recovered individuals who have been diagnosed with a PCR or antigen test less than 90 days previously). You can register through the 1808.lt system by selecting "Vaccinated or recovered persons with high-risk exposure to COVID-19 who are not subject to self-isolation".  You will have to limit the number of people you interact with for 14 days from the last day of exposure. Employed people are only advised to go to work and home if it is not possible to work remotely.

When communicating with other persons, it is recommended to wear personal protective equipment, monitor health status, measure body temperature, maintain physical distance from other persons, ensure proper hand hygiene, cough and sneeze etiquette for at least 14 days from the last day of exposure to someone with COVID-19. If symptoms characteristic of COVID-19 occur, please self-isolate immediately and register for PCR.