NACK/0x00000061/Invalid Scheduled Delivery Time error in Kannel

I have been trying to configure an SMS gateway service using Kannel and sqlbox. My system is successfully connected to the Airtel SMSC. But whenever I try to send SMS (Inserting data in send_sms table of course), I get this weird response from the SMSC

NACK/0x00000061/Invalid Scheduled Delivery Time

But I have nowhere mentioned about the scheduled delivery time. Here is the log in SMSC side

and here is my kannel configuration

#CORE
group = core
admin-port = 13000
smsbox-port = 13001
admin-password = rasello
status-password = rasello
admin-allow-ip = "*.*.*.*"
wdp-interface-name = "*"
log-file = "/var/log/kannel/bearerbox.log"
#store-file = "/var/log/kannel/kannel.store"
log-level = 0
#box-deny-ip = "*.*.*.*"
box-allow-ip = "*.*.*.*"
dlr-storage=mysql

#SMSBOX SETUP
group = smsbox
bearerbox-host = localhost
sendsms-port = 13013
bearerbox-port = 13001
log-file = "/var/log/kannel/smsbox.log"
log-level = 0

# SEND-SMS USERS
group = sendsms-user
username = username
password = password
default-smsc = rasello

#mysql connection
group = mysql-connection
id = sqlbox-db
host = localhost
port = 3306
username = root
password = N3pal@312
database = kannel
max-connections = 10

# DLR SETUP
#mysql connection
group = mysql-connection
id = mydlr
host = localhost
username = root
password = N3pal@312
database = kannel
max-connections = 10

group = dlr-db
id = mydlr
table=dlr
field-smsc=smsc
field-timestamp=ts
field-destination=destination
field-source=source
field-service=service
field-url=url
field-mask=mask
field-status=status
field-boxc-id=boxc

# SMSC SMPP
group = smsc
smsc-id = rasello
smsc = smpp
host = ip
port = port
transceiver-mode = false
smsc-username = username
smsc-password = password
system-type = smpp
interface-version = 34
address-range = ""

#SMS SERVICE GET-URL 
group = sms-service
keyword = default
send-sender = true
get-url = "http://localhost/receivesms?phone=%p&text=%a"

Please help resolving this issue

you have to contact ur SMPP provider for this coz they are rejecting your SMS with this NACK