SQL prepared statement insert into database as uppercase - php

Question

I have this function which inserts to my database some values. Values are inserted just fine but i am trying to insert them in upper case which doesn't work. If i use print_r after the for loop values are printed in uppercase. But in my database it is not stored as uppercase. Has anyone experienced an issue like this before?
function tryToInsertRow($mCurrentRowData){
global $connection;
// Make Data Uppercase
for($i = 0; $i < sizeof($mCurrentRowData); $i++){
$mCurrentRowData[$i] = strtoupper($mCurrentRowData[$i]);
}
$query_insert = "INSERT INTO main_db (contact_id, customer_code, customer_name, territory, firstname, lastname, contact_type_description, contact_is_primary, mailing_street, mailing_postal_code, mailing_city, mailing_country, email, mobile_phone, phone) VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)";
if ($stmt = mysqli_prepare($connection, $query_insert)) {
// bind parameters for markers
if (!mysqli_stmt_bind_param($stmt, "sssssssdsssssss", $mCurrentRowData[0] ,$mCurrentRowData[1] ,$mCurrentRowData[2] ,$mCurrentRowData[3] , $mCurrentRowData[4] ,$mCurrentRowData[5] ,$mCurrentRowData[6] ,$mCurrentRowData[7] ,$mCurrentRowData[8] ,$mCurrentRowData[9] ,$mCurrentRowData[10] ,$mCurrentRowData[11] ,$mCurrentRowData[12] ,$mCurrentRowData[13] ,$mCurrentRowData[14])) {
error_log(mysqli_error($connection));
return false;
}
//execute query
if (!mysqli_stmt_execute($stmt)) {
error_log(mysqli_error($connection));
return false;
}
mysqli_stmt_close($stmt);
return true;
} else {
error_log(mysqli_error($connection));
return false;
}
}
Main db creation :
CREATE TABLE `main_db` (
`contact_id` varchar(255) NOT NULL,
`customer_code` varchar(255) NOT NULL,
`customer_name` varchar(255) DEFAULT NULL,
`territory` varchar(255) DEFAULT NULL,
`firstname` varchar(255) DEFAULT NULL,
`lastname` varchar(255) DEFAULT NULL,
`contact_type_description` varchar(255) DEFAULT NULL,
`contact_is_primary` int(1) DEFAULT NULL,
`mailing_street` varchar(255) DEFAULT NULL,
`mailing_postal_code` varchar(255) DEFAULT NULL,
`mailing_city` varchar(255) DEFAULT NULL,
`mailing_country` varchar(255) DEFAULT NULL,
`email` varchar(255) DEFAULT NULL,
`mobile_phone` varchar(255) DEFAULT NULL,
`phone` varchar(255) DEFAULT NULL,
`is_processed` int(1) NOT NULL DEFAULT '0',
UNIQUE KEY `contact_id` (`contact_id`,`customer_code`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1