>>Since the value of I is 2 initially my cursor should Locate for page 3 initially and each time it should locate the data in Pageno 4 , 5 , 6 etc as the value of I increases by 1 each time.
>>But Every Time cursor is halting on Pageno=2 even though the value if I is increasing to 3,4,5 etc. What is the problem ?

As written, the AND only attaches to the "Itemized Calls" since AND takes priority. Use brackets around the ORs:

LOCATE FOR ( LEFT(STREXTRACT(POS,'(',')'),10)= '- One Time' OR ;
LEFT(STREXTRACT(POS,'(',')'),23)='- Account Level Charges' OR ; 
LEFT(STREXTRACT(POS,'(',')'),23)='Itemized Calls' );
AND Pageno=(I+1)

While you're at it- also consider using INLIST around the second two STREXTRACT() rather than repeating the STREXTRACT().

Finally, since this code effectively does a table scan for each I in your for...next unless you have indexes on all the expressions, then (depending on purpose) you might consider a SQL Select to determine which pageno meet your tests.

select pageno distinct from mytable where  LEFT(STREXTRACT(POS,'(',')'),10)= '- One Time' OR ;
LEFT(STREXTRACT(POS,'(',')'),23) in ('- Account Level Charges','Itemized Calls') where pageno>2 order by pageno into cursor mycursor