Building own Kontalk Server

Hi,

I have build our own kontalk server with domain greatdiscountsavings.com. While I am connecting to android client getting an error “Phone Number Validation failed result(0)”.
I have taken Nexmo SMS API trial and updated credentials of Nexmo in init.properties file. But problem is getting above mentioned error.
Can you please help me out of this issue or any solution to solve.
Here is the log of android client as follows:
----------------------------LOG Report---------------------------------------------------------------------

org.kontalk.debug D/SMACK: SENT (0): <stream:stream xmlns='jabber:client' to='greatdiscountsavings.com' xmlns:stream='http://etherx.jabber.org/streams' version='1.0' xml:lang='en'>
org.kontalk.debug D/SMACK: RECV (0): <?xml version='1.0'?><stream:stream xmlns='jabber:client' xmlns:stream='http://etherx.jabber.org/streams' from='greatdiscountsavings.com' id='9193894d-35dd-404c-982e-2de16c01f824' version='1.0' xml:lang='en'>
org.kontalk.debug D/SMACK: RECV (0): <
org.kontalk.debug D/SMACK: RECV (0): stream:features><sm xmlns="urn:xmpp:sm:3"/><csi xmlns="urn:xmpp:csi:0"/><mechanisms xmlns="urn:ietf:params:xml:ns:xmpp-sasl"><mechanism>EXTERNAL</mechanism></mechanisms><ver xmlns="urn:xmpp:features:rosterver"/><sub xmlns="urn:xmpp:features:pre-approval"/><roster xmlns="http://kontalk.org/extensions/roster"/><compression xmlns="http://jabber.org/features/compress"><method>zlib</method></compression></stream:features>
org.kontalk.debug D/SMACK: SENT (0): <iq to='greatdiscountsavings.com' id='B6xmt-1' type='set'><query xmlns='jabber:iq:register'><x xmlns='jabber:x:data' type='submit'><field var='FORM_TYPE' type='hidden'><value>jabber:iq:register</value></field><field label='Phone number' var='phone' type='text-single'><value>+919908020591</value></field><field label='Challenge type' var='challenge' type='text-single'><value>callerid</value></field></x></query></iq>
? I/ActivityManagerSRIB: startService caller =android.app.ApplicationThreadProxy@4383cca8, service Intent { act=com.google.android.gms.icing.proxy.ACTION_UPDATE cat=[targeted_intent_op_prefix:.icing.proxy.UpdateIcingCorporaIntentOperation] cmp=com.google.android.gms/.chimera.GmsIntentOperationService (has extras) }
? I/System.out: SRIB startService caller =android.app.ApplicationThreadProxy@4383cca8, service Intent { act=com.google.android.gms.icing.proxy.ACTION_UPDATE cat=[targeted_intent_op_prefix:.icing.proxy.UpdateIcingCorporaIntentOperation] cmp=com.google.android.gms/.chimera.GmsIntentOperationService (has extras) }
org.kontalk.debug D/SMACK: RECV (0): <
org.kontalk.debug D/SMACK: RECV (0): iq id="B6xmt-1" from="greatdiscountsavings.com" xmlns="jabber:client" type="error"><query xmlns="jabber:iq:register"><x xmlns="jabber:x:data" type="submit"><field var="FORM_TYPE" type="hidden"><value>jabber:iq:register</value></field><field var="phone" label="Phone number" type="text-single"><value>+919908020591</value></field><field var="challenge" label="Challenge type" type="text-single"><value>callerid</value></field></x></query><error code="501" type="cancel"><feature-not-implemented xmlns="urn:ietf:params:xml:ns:xmpp-stanzas"/><text xml:lang="en" xmlns="urn:ietf:params:xml:ns:xmpp-stanzas">Feature not supported yet.</text></error></iq>
org.kontalk.debug D/SMACK: SENT (0): <presence id='B6xmt-3' type='unavailable'></presence>
org.kontalk.debug D/SMACK: SENT (0): </stream:stream>
org.kontalk.debug E/NumberValidation: phone number validation failed (0)

Thanks,
Raviteja