create or alter procedure SPLIT_WORD_BY_LETTERS (
    WORD varchar(1024))
returns (
    NN integer,
    LETTER varchar(1))
AS
begin
  nn = 1;
  while ( nn <= character_length(:word) ) do
  begin
    letter = substring(:word from :nn for 1);
    suspend;
    nn = nn + 1;
  end
end

create or alter procedure FILTER_LETTERS (
    INPUT_WORD varchar(1024),
    FILTER_STRING varchar(1024))
returns (
    WORD varchar(1024))
AS
begin
  execute statement
    ('select list(letter, '''') from split_word_by_letters(:input_word) where'||:filter_string)
    (input_word := :input_word)
  into :word;
  suspend;
end

select * from filter_letters('test word и это важно for 123-45-67 it', ' upper(letter) NOT between ''А'' and ''Я'' ')

UPDATE MY_TABLE
SET 
    TEL_MOB = (select word from filter_letters(TEL_MOB , ' upper(letter) NOT between ''А'' and ''Я'' '))