Match similar special character in filters

I have to perform a search on a table with Turkish city names. The users would enter the first 4 characters of a city and I need to fetch the results from SQL. For example, user wants to find the entries for Istanbul, so he would enter ista or Ista or ISTA Problem is that Istanbul is written with special character. It is Ìstanbùl. So my query where UPPER(city) like 'UPPER()%' will not find it. It only finds it when the user enters Ìsta (with the special character). Is there a way of converting similar special character to 1 character. So for example ìíî will be converted to i. This way a user can find Ìnstanbùl with whatever variant of i they enter.